2013 beaumont site visit: management of stalk borers attacking
TRANSCRIPT
Beaumont Site Visit: Management of Stalk
Borers Attacking Sugarcane, Energycane,
Sorghum, and Rice
Project Investigators:
Graduate Assistants:
Gene Reagan, LSU AgCenter, Department of Entomology
M.O. Way, Texas A&M AgriLife Beaumont
Julien Beuzelin, LSU AgCenter, Dean Lee Research Station
Matt VanWeelden
Blake Wilson
Cooperators:
Bill White, USDA ARS Sugarcane Research Scientist
Tony Prado, Rio Grande Valley Sugar Growers Inc.
Allan Showler, USDA ARS, Kerrville, TX
and
Rebecca Pearson, Texas AgriLife Beaumont
Suhas Vyavhare, Texas AgriLife Beaumont
Randy Richard, USDA ARS Sugarcane Research Station
18 September, 2013
This work has been supported by grants from the USDA CSREES Southern Region IPM and Crops at
Risk programs, USDA NIFA AFRI Sustainable Bioenergy program, and U.S. EPA Strategic Agricultural
Initiative and Agricultural IPM programs. We also thank the Texas Rice Research Foundation, the
American Sugar Cane League, Rio Grande Valley Sugar Growers Inc, participating Agricultural Chemical
Companies, the Texas Department of Agriculture, and the Louisiana Department of Agriculture and
Forestry for their support.
COMPARISON OF STALK BORERS ATTACKING SUGARCANE AND RICE
(a) Adult female sugarcane borer (b) Sugarcane borer larva
(c) Adult female Mexican rice borer (d) Mexican rice borer larva
(e) Adult female rice stalk borer (f) Rice stalk borer larva
Photos: (a) B. Castro; (b) J. Saichuk; (c) F. Reay-Jones; (d)(e)(f) A. Meszaros
Table of Contents
Comparison of Stemborers Attacking Graminaceous Crops…………………………………….….1
Field Research Site Visit Announcement………………………………………………….………..4
Site Visit Agenda…..………………………………………………….…………………………….5
Mexican Rice Borer Establishment in Louisiana………………..…………………………………..6
Sugarcane Research
Aerial Insecticidal Control of the Mexican Rice Borer in Sugarcane, Rio Grande Valley, TX.
2012………………………………………………………………………………………….…….9
Small Plot Evaluation of Insecticidal Control of the Sugarcane Borer in
Louisiana Sugarcane, 2011………………………………………………………………………10
Evaluation of Commercial and Experimental Sugarcane Cultivars for Resistance to the Mexican
Rice Borer, Beaumont, TX, 2011 and 2012….……………………………………….………….11
Bioenergy Crops Research
Estimating Yield Loss by the Mexican Rice Borer in Sugarcane, Energycane, and
High-Biomass Sorghum…….……………………………………………..…….………....…….14
Effect of Fertilization Regime on Infestation by the Mexican Rice Borer in Bioenergy
Sorghum………………………………………………………….……………...…..…..…….…16
Sugarcane Borer Injury to Sugarcane, Energycane, and Sorghum Cultivars with
Bioenergy Potential in Louisiana…………………………………………………….………..…17
Effectiveness of the Red Imported Fire Ant in Reducing Mexican Rice Borer Injury in
Conventional and Bioenergy Cropping Systems ………………………………………………..19
Rice Research
Management of Stalk Borers in Texas Rice………………………………………………….……20
Evaluation of Insecticidal Seed Treatments for Control of Rice Water Weevil and
Stalk Borers in Early Planted Rice, Beaumont, TX, 2012……………………...………………..21
Evaluation of Insecticidal Seed Treatments and Foliar Applications for Control of Rice Water
Weevil and Stalk Borers in Water Seeded Rice, Beaumont, TX, 2012…………………..……...25
The Effect of Intertrap Distance on the Performance of Mexican Rice Borer Pheromone Traps in
Stubble Rice………………………………………………………………………..…………….29
Peer Reviewed Publications
Improved Chemical Control of the Mexican Rice Borer (Lepidoptera: Crambidae)
In Sugarcane: Larval Exposure, a Novel Scouting Method and Efficacy of a
Single Aerial Insecticide Application………………………………………………………..…..31
Oviposition and Larval Development of a Stem Borer, Eoreuma loftini, on Rice and Non-crop
Grass Hosts……………………………………………………………………………………….40
Appendices
Appendix A: Insect Nursery Site Map……………………………………………………………55
Appendix B: Bioenergy Test Plot Map……………………………………………………..……56
Appendix C: Sorghum Fertilization Test Plot Plan…………………………………………….…57
Appendix D: Host Plant Resistance Tests 2011 and 2012 Plot Plans……………………...…..…58
Appendix E: Energycane/Miscane Map…………………....……………………………..…..…..60
Texas A&M AgriLife Research and Extension Center at Beaumont
LSU AgCenter
USDA, Houma, LA
Gene Reagan, Matt VanWeelden, Blake Wilson, Julien Beuzelin, Jeff Hoy, Bill White, Ted
Wilson, Yubin Yang, Mo Way and Becky Pearson
The Beaumont Center will host a “Site Visit” on September 18, 2013 to discuss recent research
results regarding stalk borers (particularly Mexican rice borer) attacking energycane, sweet
sorghum and rice. The goal of this visit is to educate stakeholders about progress towards
managing stalk borers---particularly Mexican rice borer. Attendees will meet in the auditorium
before going to the field to observe stalk borer experiments in progress on energycane, sweet
sorghum and rice. This will be an informal visit with plenty of time for questions and discussion.
Following the field visit, attendees will again meet in the auditorium for sandwiches, snacks and
drinks while continuing to exchange information. CEUs will be provided. Below is a summary of
the details of the site visit:
Where: Beaumont Center, 1509 Aggie Dr., Beaumont, TX
When: Wednesday September 18, 2013
Time: Starts at 10am and ends about 1pm (starting later than in the past to allow attendees
to avoid overnight stay)
Contact: Mo Way, [email protected], 409-658-2186 for more information, if needed.
Please RSVP Mo by email if you plan to attend---this will help determine sandwich, snack and
drink orders.
Hope to see you September 18---drive safely!
AGENDA FOR BEAUMONT CENTER SITE VISIT
Management of Stalk Borers Attacking Energycane, Sweet Sorghum and Rice
September 18, 2013 from 10:00 to 1:00
10:00-10:15 Sign-in and introduction, Beaumont Center auditorium: Dr. Mo Way 10:15-10:25 Drive to site of energycane/sweet sorghum plots
10:25-11:30 LSU AgCenter staff (Drs. Gene Reagan, Jeff Hoy and Julien Beuzelin, and
Graduate Students Matt VanWeelden and Blake Wilson) and
USDA/Houma, LA (Dr. Bill White) will discuss distribution, identification,
life history, damage and management of Mexican rice borer relative to
current experiments; hands-on inspection of plots
11:30-11:40 Drive to energycane/miscane plots 11:40-12:00 Dr. Yubin Yang, Texas A&M AgriLife Research, will discuss
current agronomic research on energycane and miscane
12:00-12:05 Drive to rice plots 12:05-12:25 Dr. Mo Way, Texas A&M AgriLife Research, will discuss current
research on management of stalk borers in rice; hands-on inspection of
plots
12:25-12:30 Drive back to auditorium 12:30-1:00 Light lunch and further discussion of stalk borer Integrated Pest
Management (IPM) research and application 1:00 Adjourn
MEXICAN RICE BORER ESTABLISHMENT IN LOUISIANA
B.E. Wilson1, M.T. VanWeelden
1, J.M. Beuzelin
1, T.E. Reagan
1, J. Meaux
2, T. Hardy
3, and R.
Miller3
1LSU AgCenter, Department of Entomology
2LSU AgCenter, Calcasieu Parish Extension Office
3Louisiana Department of Agriculture and Forestry
Cooperative studies on the Mexican rice borer (MRB), Eoreuma loftini, between the LSU
AgCenter, Texas A&M University AgriLIFE research station at Beaumont, the Texas
Department of Agriculture, and the Louisiana Department of Agriculture and Forestry have been
on-going since 1999 to monitor the movement of this devastating pest of sugarcane into
Louisiana. As previously anticipated, MRB spread into Louisiana by the end of 2008, and was
collected in two traps near rice fields northwest of Vinton, LA on December 15. Since then,
extensive trapping of MRB has been conducted in southwest Louisiana by LDAF and LSU
AgCenter personnel. Currently, more than 100 traps are being monitored in ten Parishes in
Louisiana.
To date, pheromone traps have detected MRB moths in Calcasieu, Cameron, Jefferson
Davis, Beauregard, and Allen Parishes. The range extends from the Gulf Coast north to Oberlin,
LA and east to Jennings, LA (Fig. 1). The MRB is now present throughout Cameron and
Calcasieu Parishes and pheromone trap captures indicate substantial populations are present in
these areas (Table 1).
Additional surveys are being conducted to monitor MRB infestations in rice, sugarcane,
corn and other host crops. A MRB larval infestation was detected for the first time in a Louisiana
sugarcane field on March 29, 2013. The pest was found south of I-10 approximately 2.5 miles
west of Iowa, LA in Calcasieu Parish in a field of variety L 99-226 plant cane. While this
finding was expected as the invasive pest has been slowly approaching commercial sugarcane
production areas in Louisiana from the west for years, the detection serves as a reminder that
sugar producers across the state will soon have a new pest to consider. Larval infestations in rice
in Calcasieu Parish are reaching economically damaging levels. White heads attributable to
MRB infestations were recorded in 4% of rice shoots in fields which did not receive insecticide
seed treatments in 2013.
While the pest has been moving eastward at roughly 10 miles/year in Louisiana, recent
detection of MRB in Florida demonstrates the species’ potential for rapid expansion and
highlights the need for statewide monitoring. Due to its utilization of alternative host crops and
weedy grass hosts, control measures are not expected to be effective in stopping the eastward
spread into larger sugarcane production regions in Louisiana. Eradication of MRB is not a viable
option because of the pest’s use of non-crop hosts. Pest management decisions regarding actions
to control MRB infestations should be considered on a field-by-field basis and based on
recommended thresholds. In addition, processing sugarcane infested with MRB at the closest
mill will reduce the risk of man-assisted movement farther into the heart of the Louisiana
sugarcane production area. LSU AgCenter entomologists are continuing to research new
management strategies and provide up-to-date information regarding the risk of MRB in your
area.
The AgCenter has partnered with Pennsylvania State University to develop PestWatch, a
real-time web mapping system which will provide online access to the most current MRB
March April May June July Aug
Calcasieu 2.8 3.0 2.0 6.2 9.7 4.3
Cameron 3.5 5.1 3.5 0.9 1.8 0.9
Jeff. Davis 1.1 1.1 0.6 0.8 1.8 1.4
Allen 0.01 0.03 0.02 0.0 0.01 0
Beauregard 0.02 0.02 0.03 0.02 0.04 0.04
distribution data. The PestWatch mapping system for MRB is scheduled to be launched by June
2013 and will be openly accessible to the public. Further information on MRB biology and
management, as well as pictures to aide in identification, can be found on the LSU AgCenter
Website (http://www.lsuagcenter.com/en/crops_livestock/crops/rice/Insects/presentations/6-
Mexican-Rice-Borer.htm). If you suspect you may have an infestation of MRB or would like to
monitor a pheromone trap in your area contact LSU AgCenter Entomologists, Blake Wilson,
at [email protected], or Julien Beuzelin, at [email protected].
Table 1: Mexican rice borer pheromone trap captures in southwest Louisiana Parishes, 2013.
Data represent means of multiple traps in each parish.
Parish MRB/Trap/Day
Figure 1: Mexican rice borer distribution in SW Louisiana as of August 2013. Red pins indicate MRB positive traps, Yellow pins
indicate traps sites which have not yet detected MRB. Additional traps present in Vermillion, Rapides, Evangeline, St. Martin, and
St. Landry Parishes are not shown and have not detected MRB.
AERIAL INSECTICIDAL CONTROL OF MEXICAN RICE BORER IN SUGARCANE
RIO GRANDE VALLEY, TX, 2012
M.T. VanWeelden, B.E. Wilson, T.E. Reagan, and J.M. Beuzelin
LSU AgCenter, Department of Entomology
Evaluation of aerial application control of the Mexican rice borer (MRB), Eoreuma
loftini, in sugarcane was conducted in the Rio Grande Valley (Cameron and Hidalgo Counties)
of Texas in 2012. Insecticide treatments were randomly assigned to plots (8-10 acres/plot) in
commercial sugarcane fields of variety CP 72-1210. Pheromone traps were used to monitor
MRB populations throughout the growing season. Larval scouting was conducted by examining
100 stalks in each field on 21 Aug 2012 and revealed that infestations exceeded the threshold of
5% of stalks with treatable larvae on plant surfaces. The aerial application was made the
morning of 22 Aug by fixed wing aircraft flying at 145 mph. All treatments were applied with
10 gallons of water per acre.
MRB injury data were collected on 29 Oct 2012 from 15-stalk samples taken from 2
locations in each test plot. Differences between treatments were detected for both percent bored
internodes and adult emergence per stalk (Table 1). Mean percent bored internodes ranged from
3.36% (Belt®) to 12.64% (untreated), and mean emergence ranged from 0.13 (Prevathon
®) to
0.46 (untreated) emergence holes/stalk. Percent bored internodes in Belt and Prevathon treated
plots was significantly lower than in untreated controls. However, only Prevathon treatments
significantly reduced adult emergence per stalk. Yield data were collected by the core sampling
method and all plots were harvested completely. Two replications were harvested on 19 Dec
2013, one 8 Feb 2013, and two on 17-20 March, 2013. None of the treatments had significantly
higher yield than untreated controls (Table 1). Yield was highest in Belt®
treated plots and
lowest in Confirm®
treated plots. Further MRB injury received in treated plots after bored
internode data was collected in October is a potential explanation for the lack of differences in
yield despite having reduced injury in treated plots. The MRB remains active throughout the
winter in the Rio Grande Valley. Data indicate that new diamide chemistries, Belt® and
Prevathon®, may provide better control of the MRB than either Confirm
® or Diamond
®.
Table 1. Mexican rice borer injury and sugarcane yield. Aerial application trial, Cameron and
Hidalgo Counties, TX. 2012.
Trade
Name
Common
Name Rate (fl
oz/acre) % Bored
Emergence
/stalk
Tons of
Cane/Acre
Tons of
Sugar/Acre
Untreated NA NA 12.64a 0.46a 40.36ab 4.64a
Confirm®
Tebufenozide 16.0 7.82ab 0.32ab 33.57b 3.77b
Diamond®
Novaluron 12.0 5.62ab 0.21ab 39.07ab 4.54ab
Prevathon®
Rynaxypyr 20.0 3.55b 0.13b 41.43a 4.54ab
Belt®
Flubendiamide 4.0 3.36b 0.22ab 43.26a 4.80a
df = 4, 18.75 4, 20.62 4, 16.00 4, 16.00
F = 6.21 2.98 4.48 4.23
P= 0.0023 0.0432 0.0128 0.0159
*Means which share a letter are not significantly different (Tukey’s HSD, α = 0.05)
Treatmenta Rate (fl oz/acre) % Bored Internodes Emergence/Stalk
Control NA 20.3 B 0.72 B
Prevathon (low) 12 1.30 A 0.03 A
Prevathon (high) 20 1.20 A 0.04 A
Belt 3.0 0.92 A 0.01 A
Coragen 3.0 0.80 A 0.01 A
Confirm 8.0 0.62 A 0.03 A
Diamond 12.0 0.34 A 0.00 A
Besiege 9.0 0.09 A 0.00 A
SMALL PLOT EVALUATION OF INSECTICIDAL CONTROL OF THE SUGARCANE
BORER IN LOUISIANA SUGARCANE, 2011
B.E. Wilson, J.M. Beuzelin, M.T. VanWeelden, and T.E. Reagan
LSU AgCenter, Department of Entomology
Seven insecticide treatments in addition to an untreated control were evaluated for season
long control of the SCB in a randomized block design with five replications in a sugarcane field of
2nd
ratoon HoCP 96-540 in Burns Point, LA (St. Mary Parish). Treatment plots consisted of three
24-ft rows (0.01 acre) separated by 5-ft gaps. Two insecticide applications were made the
mornings of 5
Aug and 30 Aug when infestations exceeded the treatment threshold of 5% of stalks with borer
larvae present in leaf sheaths. Insecticides were mixed in 2 gal of water and applied using a Solo
back pack sprayer delivering 40 gallons/acre at 20 psi. Borer injury to sugarcane was assessed at
the time of harvest (5 Oct) by counting the total number of internodes (15 stalks/plot), number of
bored internodes and moth emergence holes in each stalk. Proportion of bored internodes was
analyzed using a generalized linear mixed model (Proc Glimmix, SAS Institute) with a binomial
distribution, and means were separated with Tukey’s HSD (α = 0.05). Emergence data was
analyzed using a generalized linear mixed model (Proc Glimmix, SAS Institute) with a normal
distribution.
Insecticide treatments provided substantial control and significantly reduced the proportion
of bored internodes when compared to untreated checks (F = 70.8, P <0.0001, df = 7, 587).
Percentage of bored internodes in the treated plots ranged between 0.09-1.3% compared to the
20.3% observed in the untreated check. Besiege applied at 9.0 oz/acre showed greatest reduction
in internode injury; however, differences were not detected among the insecticide treatments. Adult
emergence ranged between 0.0-0.72 emergence holes per stalk, and followed the same trend as
percentage bored internodes (F = 26.7, P <0.0001, df = 7, 586). All insecticide treatments were
significantly better than the untreated check.
Table 1: SCB injury after two insecticide applications, St. Mary Parish, LA, 2011.
aInsecticide treatments were applied with Induce surfactant at 0.5% v/v.
Means within column followed by the same letter are not significantly different (P = 0.05,
Tukey’s HSD).
EVALUATION OF COMMERCIAL AND EXPERIMENTAL SUGARCANE
CULTIVARS FOR RESISTANCE TO THE MEXICAN RICE BORER, BEAUMONT,
TX, 2011 AND 2012
T.E. Reagan1, B.E. Wilson
1, M.T. VanWeelden
1, and J.M. Beuzelin, W.H. White
2, R. Richard
2,
and M.O. Way3
11LSU AgCenter, Department of Entomology
2USDA-ARS, Sugarcane Research Unit at Houma, Louisiana
3Texas A&M AgriLIFE Research and Extension Center at Beaumont, Texas
Because of the limitations of chemical and biological control against the Mexican rice borer
(MRB), Eoreuma loftini, host plant resistance is an important part of IPM. As a control tactic,
host plant resistance can not only aid in reducing stalkborer injury, but can also reduce area-wide
populations and potentially slow the spread of the MRB. The effect of cultivars on reducing
area-wide populations is examined by comparing the number of adult emergence holes. In
addition, recent research suggests resistant cultivars which impede stalk entry and prolong larval
exposure on plant surfaces may enhance the efficacy insecticide applications (See pages 31-40).
Continued evaluation of stalkborer resistance is necessary as host plant resistance remains a
valuable tool in stalkborer IPM.
A 2-year field studies were conducted at the Texas A&M AgriLIFE Research and Extension
Center at Beaumont, TX, to assess cultivar resistance to the MRB among commercial and
experimental sugarcane cultivars in 2011 and 2012. Over both years, 33 cultivars were
evaluated. The tests included a wide variety of cultivars developed from breeding programs in St.
Gabriel, LA; Houma, LA; and Canal Point, FL. In addition, the 2012 test examined resistance in
4 biomass energy
cultivars. In both years, the tests had 1-row, 12-foot plots arranged in a randomized block design
with 5 replications (See Appendix D).
2011
The 2011 test evaluated resistance in 19 cultivars. HoCP 85-845 has been a resistant standard for many years. HoCP 04-838, which appears to have little resistance to the MRB, has recently been released to commercial growers. Experimental cultivars in the early stages of varietal development which were evaluated include: HoCP 08-726, Ho 08-706, L 08-090, L 08-088, Ho 08-711, Ho 08-717, HoL 08-723, L 08-075, L 08-092, Ho 08-709. Two energy cane varieties, L 79-1002 and Ho 02-113, were also evaluated.
Results showed significant differences (F=2.71, P= 0.0017) in injury which ranged from
1.9-17.2% bored internodes (Table 1). The most resistant cultivars examined were HoCP 85-845
and L 08-075. Experimental cultivar, L 08-075, is potentially highly resistant as it demonstrated
>8-fold reductions in MRB injury compared to susceptible cultivars. The most susceptible
cultivars were HoCP 08-726, L 08-090, and HoCP 04-838. Differences in adult emergence (F=
1.99, P =0.0187) followed the same trend as injury data ranging from 0.02-.46 emergence hole
per stalk (Table 2). Energy cane varieties showed intermediate levels of resistance.
Table 1: Borer Injury and Moth Production, Beaumont Variety Test 2011
Variety % Bored Emergence/stalk
HoCP 08-726 17.2 0.45
L 08-090 13.7 0.35
HoCP 04-838 13.4 0.28
HoL 08-723 13.1 0.10
Ho 08-711 13.1 0.46
Ho 08-717 12.4 0.20
Ho 08-706 9.5 0.18
Ho 07-613 9.0 0.27
L 79-1002 8.5 0.21
L 07-57 8.5 0.21
Ho 08-709 8.0 0.07
L 08-088 8.0 0.23
HoCP 00-950 7.9 0.08
Ho 02-113 7.7 0.08
L 08-092 7.7 0.08
Ho 05-961 7.6 0.24
HoCP 91-552 7.6 0.23
HoCP 85-845 3.9 0.10
L 08-075 1.9 0.02
*Means which share a line are not significantly different (LSD α=0.05).
2012
Resistance to the MRB was evaluated in cultivars of sugarcane, energycane, and sorghum. Commercial sugarcane varieties included were HoCP 85-845 (resistant), HoCP 05-
838 (susceptible), and Ho 05-961 (intermediate). Seven experimental cultivars from the
sugarcane variety development programs at LSU and USDA-Houma included were L 08-088, L
08-090, L 08-092, Ho 07-613, Ho 08-709, Ho 08-711, and Ho 08-717. Five sugarcane cultivars
commonly grown in the Rio Grande Valley of Texas (CP 79-1210, CP 89-2143, TCP 87-3388,
TCP 99-4474, TCP 99-4480) were also evaluated. Cultivars with potential for bioenergy
production include six energycanes (L 79-1002, Ho 02-113, Ho 07-9014, Ho 07-9017, Ho 07-
9027, and Ho 07-9076), two energy sorghums (ES 5200 and ES 5140), and one sweet sorghum
(M81E). Sugarcane and energycane cultivars were planted 26 October 2011; sorghum was
planted 19 April 2012.
On 22 October 2012, twelve randomly selected stalks were collected from each plot and the total
no. internodes, the no. bored internodes, and the no. emergence holes were recorded.
The sugarcane borer, Diatraea saccharalis, is present in the Beaumont area, however, the
stem borer population was >90% MRB in 2012. The percentage of bored internodes and no.
emergence holes per stalk were analyzed using generalized linear mixed models (Proc Glimmix,
Cultivar
Crop % Bored
Internodes
L 08-090 SC 26.47
CP 79-1210 SC 22.80
M81E SS 20.54
CP 89-2143 SC 19.29
Ho 08-717 SC 18.30
HoCP 05-838 SC 17.24
ES 5140 ES 16.81
Ho 05-961 SC 16.51
L 08-088 SC 16.35
ES 5200 ES 15.26
TCP 99-4474 SC 14.81
L 08-092 SC 14.47
Ho 08-709 SC 13.43
Ho 07-613 SC 13.38
Ho 08-711 SC 13.18
Ho 07-9014 EC 12.91
TCP 87-3388 SC 12.23
L 79-1002 EC 11.23
Ho 07-9017 EC 11.10
TCP 99-4480 SC 10.97
Ho 07-9027 EC 10.04
Ho 02-113 EC 9.55
Ho 07-9076 EC 9.03
HoCP 85-845 SC 6.01
SAS Institute) with binomial and Gaussian distributions, respectively. Results show significant
differences between cultivars (df = 23, 96; F = 14.46; P <0.0001) in percentage of bored
internodes which ranged from 6.01 to 26.47% (Table 2). Differences were also detected in the
no. emergence holes pre stalk (df = 23, 96; F = 3.05; P <0.0001) which ranged from 0.11 to 1.43
(Table 3). Consistent with results from previous evaluations, HoCP 85-845 was the least injured
(% bored) of all cultivars tested. Experimental cultivar, L 08-090, was the most susceptible in
terms of both injury and adult emergence. All of the energycane cultivars demonstrated
moderate to high levels of resistance. The three sorghum varieties demonstrated a high degree of
susceptibility.
Table 2. Mexican Rice Borer Injury Table 3. Mexican Rice Borer Moth Production
Cultivar Crop Emergence Holes/Stalk
L 08-090 SC 1.43
L 08-088 SC 1.01
CP 79-1210 SC 0.98
ES 5200 ES 0.98
HoCP 05-838 SC 0.95
CP 89-2143 SC 0.87
M81E SS 0.82
ES 5140 ES 0.77
Ho 05-961 SC 0.72
Ho 08-717 SC 0.70
TCP 99-4474 SC 0.67
Ho 08-711 SC 0.63
Ho 08-709 SC 0.55
Ho 07-613 SC 0.55
L 08-092 SC 0.47
TCP 99-4480 SC 0.46
Ho 07-9014 EC 0.32
TCP 87-3388 SC 0.28
Ho 02-113 EC 0.28
HoCP 85-845 SC 0.23
Ho 07-9027 EC 0.23
L 79-1002 EC 0.20
Ho 07-9076 EC 0.14
Ho 07-9017 EC 0.11
*SC = Sugarcane, EC = Energycane, ES = Energy Sorghum, SS = Sweet Sorghum
**Means which share a line are not significantly different (Tukey’s HSD, α = 0.05)
ESTIMATING YIELD LOSS BY THE MEXICAN RICE BORER IN SUGARCANE,
ENERGYCANE AND HIGH-BIOMASS SORGHUM
M.T. VanWeelden1, B.E. Wilson
1, J.M. Beuzelin
1, T.E. Reagan
1, and M.O. Way
2
1LSU AgCenter, Department of Entomology
2Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
The Mexican rice borer (MRB), Eoreuma loftini, is an invasive stem-borer, which poses a
threat to crops grown for biofuel production in the Gulf Coast Region. An experiment was
conducted in 2012 at the Texas A&M AgriLIFE Research and Extension Center in Beaumont to
evaluate yield loss by the MRB among varieties of sugarcane, energycane, and energy sorghum.
Two sugarcane varieties (HoCP 04-838 and HoCP 85-845) and two energycane varieties (L 79-
1002 and Ho 02-113) were evaluated. Two high-biomass sorghum varieties (ES
5200 and ES 5140) and one sweet sorghum variety (M81E), which have potential for biofuel
production, were also evaluated. The experiment was arranged using a split-plot design with
four replications (Appendix B). Replications consisted of seven, 3-row plots (72 ft long, 5.25 ft
row spacing). Crop varieties were randomized to plot. Plots were further divided into four, 3-
row subplots (18 ft long) and subjected to one of four MRB infestation levels: protected
(biweekly application of tebufenozide), natural infestation, enhanced infestation, and highly-
enhanced infestation. To achieve enhanced infestation levels, MRB egg masses (~30 eggs) were
clipped to the basal leaves of each plant. Three 4-stalk samples were collected from each
subplot at the end of the season and the no. bored internodes and emergence holes were
recorded. Stalks were weighed and crushed to calculate total sugar, dry weight, and theoretical
ethanol output. Theoretical
ethanol output was calculated using methods described by Vasilakoglou et al. (2011, Field Crops
Res. 120: 38-46).
Differences were detected in the percentage of bored internodes across variety,
infestation level, and variety by infestation level (Table 1). Tebufenozide was successful in
suppressing injury to < 1.0% bored internodes in all subplots subjected to protected infestation
levels. In subplots with highly-enhanced infestations, the percentage of bored internodes ranged
from 9.1–26.8%, with varieties of energycane (L 79-1002 and Ho 02-113) and sweet sorghum
(M81E) expressing higher levels of resistance. In terms of yield, differences in wet weight per
stalk were detected across varieties and infestation levels. Higher infestations were associated
with a decrease in wet weight for all varieties. A negative impact in yield was also evident in
terms of theoretical ethanol production, as decreases in ethanol productivity were observed with
enhanced infestations. In highly-enhanced infestations, decreases in ethanol production ranged
from 12–42% when compared to suppressed subplots. For both conventional and bioenergy
varieties, maximum ethanol productivity was achieved in MRB-protected subplots.
Results from this study demonstrate that the MRB has potential to reduce yield in
bioenergy crops. Current IPM practices will need to be implemented into bioenergy cropping
systems in order to reduce yield-losses under high borer pressure.
Table 1: Mexican rice borer injury and yield parameters for sugarcane, energycane, high-
biomass sorghum, and sweet sorghum varieties with varying infestation levels (1=control,
2=natural, 3=enhanced, 4=highly-enhanced). Replicated field trial, Beaumont, TX, 2012.
Variety Infestation Level Percent Bored
Internodes
Weight (kg)/Stalk Theoretical Ethanol
Output (L/ha)
Energycane
L 79-1002
Energycane
Ho 02-113
Sugarcane
HoCP 04-838
Sugarcane
HoCP 85-845
High-biomass Sorghum
ES 5200
High-biomass Sorghum
ES 5140
Sweet Sorghum
M81E
Type III Test of Fixed
Effects
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
Variety
Infestation Level
Variety*
Infestation Level
0.0
4.0
13.0
9.4
0.0
2.7
6.0
10.3
0.1
18.1
28.4
21.9
0.7
5.8
26.8
22.1
0.0
23.5
10.9
26.8
0.0
13.2
12.0
19.4
0.5
11.4
7.2
9.1
F = 3.29
P = 0.0230
F = 31.31
P < 0.0001
F = 2.71
P = 0.0019
0.54
0.33
0.27
0.29
0.35
0.34
0.27
0.23
0.71
0.64
0.52
0.43
0.79
0.58
0.46
0.42
0.66
0.59
0.54
0.52
0.33
0.26
0.23
0.23
0.28
0.22
0.14
0.17
F = 20.06
P < 0.0001
F = 27.28
P < 0.0001
F = 1.41
P = 0.1579
26882.0
16485.0
18658.0
19931.0
23008.0
20456.0
17755.0
19815.0
15041.0
12765.0
12323.0
10478.0
9396.4
7725.9
7201.4
7978.5
41997.0
25758.0
31471.0
30501.0
21538.0
14413.0
13413.0
14675.0
16920.0
11754.0
10835.0
9922.6
F = 28.86
P < 0.0001
F = 18.59
P < 0.0001
F = 1.49
P = 0.1251 This research work is a portion of the Ph.D. program of study by Matthew VanWeelden in the
LSU Department of Entomology.
SUGARCANE BORER INJURY TO SUGARCANE, ENERGYCANE, AND SORGHUM
CULTIVARS WITH BIOENERGY POTENTIAL IN LOUISIANA
B.E. Wilson, M.T. VanWeelden, T.E. Reagan, and J.M. Beuzelin
LSU AgCenter, Department of Entomology
The U.S. Gulf Coast is among the geographic regions with the highest potential for
production of dedicated cellulosic bioenergy crops, especially energycane and high-biomass
sorghum. The most destructive pest of sugarcane in Louisiana is the sugarcane borer (SCB),
Diatraea saccharalis, which also attack graminaceous bioenergy crops. However, the potential
of this pest to cause yield losses in bioenergy crops remains unknown. This study examines the
effect of SCB injury under natural pest pressure and associated yield loss in sugarcane,
energycane, high-biomass sorghum, and sweet sorghum in two locations in Louisiana.
Cultivars which were evaluated include SCB resistant sugarcane (HoCP 85-845),
susceptible sugarcane (HoCP 00-950), two energycanes (L 79-1002 and Ho 02-113), sweet
sorghum (M81E), and two high-biomass sorghums (ES 5200 and ES 5140). Cultivars were
evaluated in replicated field studies in Rapides Parish (2011 and 2012) and St. Mary Parish
(2012). Plots of
each variety were divided into protected (biweekly applications of tebufenozide) and unprotected
(no insecticides) subplots. The crop production area around the Rapides Parish field site (near
Cheneyville, LA) consists of a diverse mosaic of multiple row crops including corn, grain
sorghum, sugarcane, rice, soybeans, and cotton. The area surrounding the St. Mary Parish
location (near Burns Point, LA) is entirely devoted to sugarcane production.
Natural populations of SCB in Rapides Parish in 2011 were very low and percentage of
bored internodes averaged < 1.0% in all cultivars. SCB infestations in unprotected plots in
Rapides Parish in 2012 (1.2–7.1% bored internodes) were slightly higher than in 2011, and
significant differences were detected among cultivars (Table 1). Mean borer injury was greater
than 5-fold higher at the St. Mary Parish location than in Rapides Parish in 2012. SCB injury to
unprotected plots in St. Mary Parish in 2012 (Table 2) ranged from 3.4% (HoCP 85-845) to
17.7% bored internodes (HoCP 00-950). Differences were detected (P < 0.001) in both
percentage of bored internodes and number of adult emergence holes among cultivars.
Tebufenozide applications were effective in reducing SBC injury to <1% bored for all cultivars
evaluated, and protected plots were used to calculate yield loss attributable to SCB injury. Yield
loss was based on the difference in mean stalk weight between protected and unprotected plots
of each cultivar. Yield loss (Table 2) was greatest in sweet sorghum M81E (26.1%) and least in
energycane Ho 02-113 (5.9%). High-biomass sorghums suffered yield losses of 22–24%.
Energycane Ho 02-113 is relatively resistant to SCB.
Results from these studies demonstrate that natural levels of SCB infestations have
potential to cause substantial yield loss in bioenergy crops. Host plant resistance will continue to
be important to SCB management in bioenergy and conventional crops. Levels of resistance are
crop- and cultivar-specific. Insecticidal protection including development of cultivar-specific
thresholds will be required to achieve maximum yields. Additionally, a landscape approach
must be used to assess the interactive role of pest management in conventional and bioenergy
crops.
Table 1: SCB injury to unprotected plots, Rapides Parish, LA, 2012.
% Bored internodes No. emergence
holes/Stalk
High-biomass
Sorghum
ES 5140 1.7 b 0.08
ES 5200 1.2 b 0.07
Sweet Sorghum M81E 7.1 a 0.33
L 79-1002 2.8 ab 0.14 Energycane
Sugarcane
Ho 02-113 1.2 b 0.05
HoCP 00-950 3.5 ab 0.12
HoCP 85-845 1.4 b 0.02
F-value; P > F F = 3.2; P = 0.017 F = 2.4; P = 0.059
*Means followed by the same a letter are not different (Tukey’s HSD, α = 0.05)
Table 2: SCB injury to unprotected plots and associated yield loss, St. Mary Parish, LA, 2012.
% Bored
internodes No. emergence
holes/Stalk % Yield Loss
High-biomass
Sorghum
ES 5140 10.1 abc 0.34 b 22.4 ab
ES 5200 16.2 a 0.90 b 24.3 a
Sweet Sorghum M81E 14.6 ab 0.75 b 26.1 a
L 79-1002 11.1 abc 0.79 b 10.5 bc Energycane
Sugarcane
Ho 02-113 5.1 bc 0.39 b 5.8 c
HoCP 00-950 17.7 a 1.90 a 18.8 abc
HoCP 85-845 3.4 c 0.22 b 9.0 b
F-value
P > F
F = 6.0
P < 0.001
F = 9.1
P < 0.001
F = 7.6
P < 0.001
*Means followed by the same a letter are not different (Tukey’s HSD, α = 0.05)
EFFECT OF FERTILIZATION REGIME ON INFESTATION BY THE MEXICAN
RICE BORER IN BIOENERGY SORGHUM
M.T. VanWeelden1, B.E. Wilson
1, J.M Beuzelin
1, T.E. Reagan
1, and M.O. Way
2
1LSU AgCenter, Department of Entomology
2Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
A study was initiated in 2013 at the Texas A&M AgriLIFE Research and Extension
Center in Beaumont, Texas to assess the impact of nitrogen fertility on infestation by the
Mexican rice borer (MRB), Eoreuma loftini, in varieties of sorghum used in production of
biofuels. Two varieties of high-biomass sorghum (ES 5200 and ES 5140) and one variety of
sweet sorghum (M81E) were evaluated in this experiment. The experiment was arranged using
split-plot design with four replications. Replications consisted of four, 6-row plots (75 ft long, 3
ft row spacing). Four nitrogen rates (0, 40, 80, or 120 lbs N/acre) were randomized to plots.
Plots were further divided into three, 2-row subplots, which were assigned to sorghum varieties.
Prior to planting, soil samples were collected in fifteen random locations across the field and sent
to the LSU AgCenter Soil Testing and Plant Analysis Lab to determine preexisting nitrogen
levels. Urea was applied to the soil by hand immediately after planting.
Plants are currently being checked on a regular schedule for MRB-related injury. In
addition, minor pests such as aphids and armyworms will be monitored throughout the growing
season. Since early June, populations of the sugarcane aphid, Melanaphis sacchari, have been
high throughout the entire test, though most damage remains exclusively on M81E and ES 5140.
An application of Carbine was made in July for control of aphids. This experiment will be
conducted in varieties of sugarcane and energycane starting next season. This research work is a portion of the Ph.D. program of study by Matthew VanWeelden in the LSU
Department of Entomology.
EFFECTINESS OF THE RED IMPORTED FIRE ANT IN REDUCING MEXICAN RICE
BORER INJURY IN CONVENTIONAL AND BIOENERGY CROPPING SYSTEMS
M.T. VanWeelden1, B.E. Wilson
1, J.M Beuzelin
1, T.E. Reagan
1, and M.O. Way
3
1LSU AgCenter, Department of Entomology
2Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
A study was conducted in 2012 at the Texas A&M AgriLIFE Research and Extension
Center in Beaumont, TX to assess the effect of predation by the red imported fire ant, Solenopsis
invicta, on field populations of Mexican rice borer (MRB), Eoreuma loftini. The experiment was
arranged in a randomized complete block design with four replications. Each replication consisted
of seven 3-row plots measuring 72 ft in length. The following seven varieties were randomized to
plot: two sugarcanes (HoCP 04-838 and HoCP 85-845), two energycanes (L 79-1002 and Ho 02-
113), two high-biomass sorghums (ES 5200 and ES 5140), and one sweet sorghum (M81E).
Pitfall traps were inserted into the center of each plot and contents were collected biweekly in
order to estimate fire ant populations. To establish a heterogeneous distribution of ant populations,
a granule bait insecticide consisting of hydromethylnon and S-methoprene was applied at random
throughout the field. To determine total MRB injury at the end of the season, MRB injury (%
bored internodes and no. of emergence holes) was recorded on 12 randomly selected plants (4 per
row) from each plot using destructive sampling. The ratio of total emergence over percent bored
internodes was calculated for each plot to determine relative survival of the MRB. The
relationship between fire ant trap counts and MRB relative survival was analyzed for each variety
using multiple linear regression (Proc Reg, SAS Institute).
A relationship between fire ant trap counts and MRB relative survival was detected across
all varieties (F=8.13; P<0.0001; R2=0.6329). Additionally, the impact of ants was found to be
statistically significant (t=2.72; P=0.0103), decreasing relative survival of the MRB by a
magnitude of 0.16 per 1 unit (fire ants) increase in trap counts. In the absence of fire ants, relative
survival of the MRB ranged from 13.06–49.43%, with varieties of MRB-susceptible sugarcane
(HoCP 04-838) and energycane (L 79-1002 and HoCP 02-113) expressing the highest and lowest
levels of MRB survival, respectively.
This data suggests that red imported fire ants have the potential to suppress MRB
infestations in sugarcane, energycane, high-biomass sorghum, and sweet sorghum, however not at
the extent as with the sugarcane borer, Diatraea saccharalis. In conjunction with MRB resistant
cultivars, natural enemies can be used as an additional tool to mitigate crop losses against stalk
boring pests. Additional studies will need to be conducted to determine more specifically the
stages of MRB development which are at most risk to predation by fire ants, as well as the
combined effects of other predators and parasitoids.
This research work is a portion of the Ph.D. program of study by Matthew VanWeelden in the LSU
Department of Entomology.
MANAGEMENT OF STALK BORERS IN RICE
Mo Way, Becky Pearson, Caleb Verret and Suhas Vyavhare
Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
---Mexican rice borer (MRB), sugarcane borer (SCB) and rice stalk borer attack Texas rice
---MRB now appears to be most abundant stalk borer attacking Texas rice
------First found in Texas Rice Belt in 1988; has since spread throughout the Texas Gulf Coast
and now threatens rice and sugarcane industries in Louisiana
---Can capture moths in pheromone traps as soon as rice is planted, but little or no MRB
activities in field until about panicle differentiation ---Avoid planting late
---Ratoon crop also vulnerable
---Lower cutting height of main crop can reduce populations and damage on ratoon crop
---Control grass weeds in and around field
---Certain areas of Texas Rice Belt (Jackson and Matagorda Counties) more prone to stalk borer
damage, but other areas also vulnerable
---Encourage vigorous stand (thin stands and levee rice are vulnerable) ---Hybrids appear to be more resistant than inbreds (future research need)
---Apply pyrethroids at 1-2 inch panicle followed by another application at heading
---Use Dermacor X-100 seed treatment
---Control of stalk borers on main crop benefits both main and ratoon crops
---Bt rice effective
FOR MORE INFORMATION SEE THE TEXAS RICE PRODUCTION
GUIDELINES https://beaumont.tamu.edu/eLibrary/Bulletins/2012_Rice_Production_Guidelines
OR CONTACT MO WAY [email protected] 409-658-2186
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
EVALUATION OF INSECTICIDAL SEED STREATMENTS FOR CONTROL OF RICE
WATER WEEVIL AND STALK BORERS IN EARLY PLANTED RICE, BEAUMONT,
TX, 2012
Mo Way, Becky Pearson, Caleb Verret and Suhas Vyavhare
Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
← North PLOT PLAN
I II III IV
1 4 10 2 19 9 28 1
2 6 11 1 20 5 29 4
3 3 12 6 21 7 30 5
4 9 13 8 22 3 31 2
5 5 14 9 23 6 32 8
6 2 15 3 24 2 33 3
7 8 16 4 25 1 34 7
8 1 17 7 26 8 35 9
9 7 18 5 27 4 36 6 Plot size: 7 rows, 7 inch row spacing, 18 ft long, with barriers on reps I and III Variety: CL162 (provided by Horizon Ag) and XP753 (provided by RiceTec)
Note: smaller numbers in italics are plot numbers
TREATMENT DESCRIPTIONS, RATES AND TIMINGS
Treatment no. Variety Description Rate
1 CL162 Dermacor X-100a 2.5 fl oz/cwt
2 CL162 Dermacor X-100a 1.75 fl oz/A
3 CL162 CruiserMaxx Rice 7 fl oz/cwt
4 CL162 Untreated ---
5 XP753 Dermacor X-100a 4 fl oz/cwt
6 XP753 Dermacor X-100a 5 fl oz/cwt
7 XP753 Dermacor X-100a 1.75 fl oz/A
8 XP753 CruiserMaxx Rice 7 fl oz/cwt
9 XP753 Untreated --- a
Also contains Maxim 4FS @ 0.30 µg ai/seed, Dynasty 0.83FS @ 1.50 µg ai/seed and Apron
XL @ 1.90 µg ai/seed
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Agronomic and Cultural Information Experimental design: Randomized complete block with 9 treatments and 4 replications
Planting: Drill-planted test @ 50 lb/A (CL162) and 20 lb/A (XP753) into League soil (pH
5.5, sand 3.2%, silt 32.4%, clay 64.4%, and organic matter 3.8 - 4.8%) on Apr 27
Plot size = 7 rows, 7 inch row spacing, 18 ft long with metal barriers on reps I and
III
Emergence on May 6 Irrigation: Flushed blocks (temporary flood for 48 hours, then drain) on Apr 29
Note: Plots were flushed as needed from emergence to permanent flood
Permanent flood (PF) on May 26 (20 days after emergence) Fertilization: All fertilizer (urea) was distributed by hand.
34 lb N/A (20% of 170) on CL162 only on Apr 29 at planting
85.0 lb N/A (50% of 170) on CL162 on May 26 at PF
120 lb N/A on XP753 on May 26 at PF
51.0 lb N/A (30% of 170) on CL162 only on Jun 11 at panicle differentiation
60 lb N/A on XP753 on Jul 16 at late boot/early heading
Herbicide: Permit @ 1 oz/A, Command 3ME @ 1 pt/A and RiceBeaux @ 3 qt/A applied
with a 2-person hand-held spray boom (13- 80015 nozzles, 50 mesh screens, 16
gpa final spray volume) on May 16 for early season weed control Treatments: All seed treatments applied by Entomology project on Apr 24
Sampling: Stand counts (3, 3 ft counts on rows 2, 4 and 6) on May 10
Vigor ratings on May 14; no signs of insect damage other than rice water weevil
(RWW) feeding scars
Vigor ratings on May 23; some phyto (possibly from herbicide) in all plots,
seems worse in XP753 than in CL162
RWW cores (5 cores per plot, each core 4 inches diameter, 4 inches deep,
containing at least one rice plant) were collected on Jun 19 and Jun 28. Core
samples were stored in a cold room, later washed through 40 mesh screen
buckets and immature RWW counted.
Whiteheads (WHs) counted in 4 rows per plot on Jul 26; WHs are a measure of
stalk borer activity.
Harvest: Harvested all plots on Sep 14
Size harvested plot = 7 rows, 7 inch row spacing, 18 ft long
Data analysis: RWW and WH counts transformed using x + 0.5 ; yields converted to 12% moisture; all data analyzed by ANOVA and means separated by LSD.
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Rice plant stands were higher in CL162 than XP753 plots, as expected (Table 1). Within a
variety, plant stands were not significantly different among treatments; thus, the seed
treatments did not affect rice plant stands. Vigor ratings were lowest in the untreated, regardless of
variety. So, in general, plants derived from treated seed appeared more “robust” than plants in
untreated plots. Vigor ratings were somewhat subjective and included color, uniformity of stand
and general appearance.
RWW densities on the 1st
sample date were very high in untreated plots of both varieties
(Table 2). However, untreated XP753 produced higher numbers of RWW compared to untreated
CL161 which is not surprising because RWWs prefer thin to thick stands of rice. The lower rates
of Dermacor X-100 performed as well as the higher rates for both varieties (seeding rates).
Results were similar for the 2nd
sample date. CruiserMaxx Rice did not perform as well as
Dermacor X-100, regardless of variety/seeding rate. In addition, for CL162, Dermacor X-100
rates significantly reduced WH densities. The majority of stalk borers were Mexican rice borer.
No significant populations of other insects were observed during the course of the experiment.
XP753 produced higher yields than CL162 across all treatments. For CL162, the average yield
increase for the seed treatments compared to the untreated was more than 800 lb/A. For XP753, the
average yield increase for the seed treatments compared to the untreated was more than 1,100 lb/A.
Table 1: Mean stand and vigor data for Dermacor X-100 seed treatment rate study (early
planting). Beaumont, TX, 2012.
Variety Treatment
Rate
(fl oz/cwt)
Stand
(plants/ft of
row)
Vigor rating (1 – 9)a
May 14 May 23
CL162 Dermacor X-100b
2.5 8.4 a 5.3 c 6.3 ab
CL162 Dermacor X-100b
1.75 fl oz/A 7.9 a 5.3 c 6.0 ab
CL162 CruiserMaxx Rice 7 8.4 a 6.8 a 6.8 a
CL162 Untreated --- 7.9 a 5.0 c 5.0 c
XP753 Dermacor X-100b
4 4.8 b 5.3 c 6.0 ab
XP753 Dermacor X-100b
5 5.1 b 5.0 c 5.8 bc
XP753 Dermacor X-100b
1.75 fl oz/A 3.8 b 5.3 c 5.5 bc
XP753 CruiserMaxx Rice 7 4.2 b 6.0 b 5.8 bc
XP753 Untreated --- 4.9 b 5.0 c 5.0 c a
Scale of 1 – 9: 1 = visually and clearly inferior to untreated; 2 = significantly inferior; 3 =
noticeably inferior; 4 = slightly inferior; 5 = equal to; 6 = slightly better; 7 = noticeably better; 8
= significantly better; and 9 = visually and clearly better than untreated. b
Also contains Maxim 4FS @ 0.30 µg ai/seed, Dynasty 0.83FS @ 1.50 µg ai/seed and Apron XL @ 1.90 µg ai/seed
Means in a column followed by the same letter are not significantly different (P = 0.05, ANOVA
and LSD)
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Table 2. Mean rice water weevil (RWW), whitehead and yield data for Dermacor X-100 seed
treatment rate study. Beaumont, TX. 2012.
Variety
Treatment
Rate
(fl oz/cwt)
RWWa/
Jun 19
5 cores
Jun 28
WHsa/4
rows
Yield
(lb/A)
CL162 Dermacor X-100b 2.5 8.3 cd 2.5 d 0.0 c 6964 cd
CL162 Dermacor X-100b 1.75 fl oz/A 6.5 d 2.3 d 0.3 c 7238 c
CL162 CruiserMaxx Rice 7 23.5 bc 7.8 bcd 13.5 a 6953 cd
CL162 Untreated --- 81.8 a 21.8 a 6.5 b 6234 d
XP753 Dermacor X-100b 4 8.0 cd 14.3 abc 0.0 c 9894 a
XP753 Dermacor X-100b 5 8.3 cd 5.3 cd 0.3 c 9892 a
XP753 Dermacor X-100b 1.75 fl oz/A 5.0 d 3.3 d 0.0 c 10232 a
XP753 CruiserMaxx Rice 7 38.5 b 17.5 ab 0.0 c 9666 ab
XP753 Untreated --- 100.3 a 26.3 a 0.5 c 8794 b a
RWW = rice water weevil; WH = whitehead b
Also contains Maxim 4FS @ 0.30 µg ai/seed, Dynasty 0.83FS @ 1.50 µg ai/seed and Apron
XL @ 1.90 µg ai/seed
Means in a column followed by the same letter are not significantly different (P = 0.05, ANOVA
and LSD)
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
EVAULUATION OF INSECTICIDAL SEED TREATMENTSA AND FOLIAR
APLLICATIONS FOR CONTROL OF THE RICE WATER WEEVIL AND STALK
BORERS IN WATER SEEDED RICE, BEAUMONT, TX, 2012
Mo Way, Becky Pearson, Caleb Verret and Suhas Vyavhare
Texas A&M AgriLIFE Research and Extension Center, Beaumont, TX
← North PLOT PLAN
I II III IV
1 3 9 7 17 8 25 6
2 8 10 5 18 4 26 1
3 1 11 3 19 6 27 8
4 4 12 8 20 7 28 2
5 6 13 2 21 1 29 5
6 2 14 4 22 3 30 7
7 7 15 6 23 5 31 3
8 5 16 1 24 2 32 4 Plot size: 4 ft x 18 ft long, with barriers
Variety: CL162 (provided by Horizon Ag) and Presidio (provided by TRIA)
Note: smaller numbers in italics are plot numbers
TREATMENT DESCRIPTIONS, RATES AND TIMINGS
Rate
Treatment no. Variety Description (fl oz/cwt)
1 Presidio Dermacor X-100 2
2 Presidio Dermacor X-100 1.75
3 Presidio Karate Za
0.03 lb ai/A
4 CL162 Dermacor X-100 3
5 CL162 Dermacor X-100 2.5
6 CL162 Karate Za
0.03 lb ai/A
7 CL162 Untreated ---
8 Presidio Untreated --- a
Karate Z foliar treatments applied 3 days after rice emergence through water
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Agronomic and Cultural Information Experimental design: Randomized complete block with 8 treatments and 4 replications
Planting: Broadcast (Presidio @ 100lb/A, and CL162 @ 70 lb/A) by hand into flooded
plots containing League soil (pH 5.5, sand 3.2%, silt 32.4%, clay 64.4%, and
organic matter 3.8 - 4.8%) on May 31
Plot size = 4 ft x 18 ft long with metal barriers
Emergence through water on Jun 9 Irrigation: Permanent flood (PF) on May 29 (continuous flood regime)
Fertilization: All fertilizer (urea) was distributed by hand.
113.3 lb N/A (2/3 of 170) on May 29 at planting
56.7 lb N/A (1/3 of 170) on Jul 6
Herbicide: Londax @ 1.5 oz/A applied using a hand-held, CO2 pressurized, 3 nozzle
(800067 tips with 50 mesh screens, 29 gpa final spray volume) spray rig on Jul 2, for duck salad control
Treatments: Treatments 1, 2, 4 and 5 (Dermacor X-100 seed treatments) applied by the
Entomology Project
Treatments 3 and 6 (Karate Z foliar spray) applied using a hand-held, CO2
pressurized, 3 nozzle (800067 tips with 50 mesh screens, 29 gpa final spray
volume) spray rig on Jun 12 (3 days after emergence through water) Sampling: Floating seedlings removed and counted on Jun 11
Vigor ratings; no phyto noted; poor stand on south end of plot 29 on Jun 16
Vigor ratings; no phyto noted; poor stand on south end of plot 29 on Jun 22
5, 0.34ft2
stand counts per plot on Jul 2
Vigor ratings; no phyto noted; poor stand on south end of plot 29 on Jul 3
Rice water weevil (RWW) cores (5 cores per plot, each core 4 inches diameter, 4
inches deep, containing at least one rice plant) were collected on Jul 2 and Jul
11. Core samples were stored in a cold room, later washed through 40 mesh
screen buckets and immature RWW counted.
Whiteheads (WHs) counted in each plot on Sep 3; WHs are a measure of stalk
borer activity.
Harvest: Harvested all plots on Sep 10
Size harvested plot = 4 ft wide, 18 ft long
Data analysis: RWW and WH counts transformed using x + 0.5 ; yields converted to 12% moisture; all data analyzed by ANOVA and means separated by LSD
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Dislodged seedlings (floaters) were observed in selected plots about the time of rice
emergence through water. Previous research implicated a small aquatic beetle, Tropisternus
lateralis, responsible for dislodging seedlings through foraging, feeding and reproductive activities.
Other factors, such as wind and tadpole shrimp, also can cause uprooting of seedlings. However,
tadpole shrimp do not occur in Texas rice paddies. Very high numbers of floaters were found in
untreated and Karate Z-treated plots (Table 1). This suggests Dermacor X-100 seed treatments
prevented T. lateralis from uprooting rice. The seed treatment probably killed populations of this
aquatic insect. In addition, T. lateralis was observed in plots with an abundance of floaters. Karate
Z treatments were probably not effective because applications were made at rice emergence
through water. Prior to this time, seedlings were probably uprooted by T. lateralis.
Although the number of floaters was significantly different among treatments, rice plant
stands were not. Vigor ratings were visual and based on color, height, uniformity and general
plant health. The most vigorous appearing plot in a replication was assigned a vigor rating of 9;
all other plots in this replication were rated relative to the highest rated plot. Vigor ratings were
similar among treatments 7 days after rice emergence through water. However, 13 and 23 days after
rice emergence through water, generally, untreated plots of both varieties exhibited the least vigor.
Due to the late planting date, RWW populations were relatively low in untreated plots
(Table 2). However, WH counts were very high in untreated plots of CL162. Data suggest
CL162 is very susceptible to stalk borer damage. The majority of stalk borers were Mexican rice
borer. Yields were relatively low throughout the experiment---again, due to the late planting
date. In addition, Presidio produced higher yields than CL162 which may be due to lower stalk
borer pressure in Presidio versus CL162.
Table 1: Mean floater, vigor and stand data for Dermacor X-100 water-seeded study. Beaumont,
TX, 2012.
Rate
Floaters/
Stand Vigor ratings (1 – 9)
Variety Treatment (fl oz/cwt) plot (plants/ft2) Jun 16 Jun 22 Jul 2
Presidio Dermacor X-100 2 1.5 c
Presidio Dermacor X-100 1.75 1.8 c
Presidio Karate Z 0.03 lb ai/A 356.5 a
30.0 a 9.0 9.0 a 9.0 a
30.8 a 9.0 9.0 a 8.8 a
31.8 a 9.0 9.0 a 8.5 ab
CL162 Dermacor X-100 3 1.3 c 21.6 b 9.0 8.3 ab 8.5 ab
CL162 Dermacor X-100 2.5 4.8 c 21.1b 8.5 7.8 b 8.0 ab
CL162 Karate Z 0.03 lb ai/A 197.3 ab 22.4 b 9.0 9.0 a 8.8 a
CL162 Untreated --- 166.5 b 21.7 b 9.0 8.5 ab 7.5 bc
Presidio Untreated --- 386.5 a 32.8 a 9.0
NS
8.5 ab 6.5 c
Means in a column followed by the same or no letter are not significantly (NS) different (P = 0.05, ANOVA and LSD).
M.O. Way [email protected] (409)752-2741 ext.2231 Texas A & M AgriLife Research and Extension Center at Beaumont 1509 Aggie Dr. Beaumont, TX 77713 http://beaumont.tamu.edu
Table 2: Mean rice water weevil (RWW), whitehead and yield data for Dermacor X-100 water-
seeded study. Beaumont, TX, 2012.
Rate RWW/5 cores
Yield
Variety Treatment (fl oz/cwt) Jul 2 Jul 11 WHs/plot (lb/A)
Presidio Dermacor X-100 2 9.0 5.5 bc 7.5 c 5490 ab
Presidio Dermacor X-100 1.75 15.3 9.0 bc 5.3 c 5831 a
Presidio Karate Z 0.03 lb ai/A 23.5 16.3 a 10.5 c 5517 ab
CL162 Dermacor X-100 3 7.8 3.8 c 32.5 b 5316 abc
CL162 Dermacor X-100 2.5 7.0 9.3 ab 31.0 b 4983 abc
CL162 Karate Z 0.03 lb ai/A 14.8 6.0 bc 38.0 b 4877 abc
CL162 Untreated --- 18.3 8.3 bc 64.0 a 4311 c
Presidio Untreated --- 16.3 6.8 bc 8.5 c 4530 bc
NS
Means in a column followed by the same or no letter are not significantly (NS) different (P = 0.05, ANOVA and LSD).
This research work is a portion of the Ph.D. program of study by Blake Wilson in the LSU
Department of Entomology. .
THE EFFECT OF INTERTRAP DISTANCE ON THE PERFORMANCE OF MEXICAN
RICE BORER PHEROMONE TRAPS
B.E. Wilson1, J.M. Beuzelin
1, M.T. VanWeelden
1, T.E. Reagan
1, and J. Allison
2
1LSU AgCenter, Department of Entomology
2Canadian Forestry Service (formerly LSU AgCenter)
The Mexican rice borer (MRB), Eoreuma loftini, is an invasive stalk borer from Mexico
which is expected to cause major economic losses to the sugarcane and rice crops in Louisiana.
Traps baited with MRB female sex pheromone are effective tools to monitor range expansion and
assist scouting for the pest in sugarcane. Traps are currently placed 10 parishes in Western
Louisiana to monitor MRB populations. However, the attractive distance, or active space,
remains unknown. The active space is the area downwind of a pheromone source over which
males are able to detect and respond to the pheromone. A study was conducted in Oct–Nov 2011
to assess the active space of pheromone traps by examining the effect of intertrap distance on the
number of male MRB captured.
The effect of intertrap distance was assessed with hexagonal arrays of pheromone traps
with a single trap in the center (Figure 1). Arrays with intertrap distances of 5, 25, 50, 100 and
250 m were deployed in rice fields on two farms in Jefferson and Chambers Counties, TX, and the
number of moths caught was recorded for all traps for 5 sampling periods for a total of 10
replications. The number of moths caught per trap/day and the proportion of moths caught by the
center trap versus perimeter trap were analyzed using generalized linear mixed models (Proc
Glimmix SAS 2008). Differences were detected between treatments (F = 16.9, P < 0.0001), with
the greatest numbers of MRB caught in traps with an intertrap distance of 250 m (Table 1). The
proportion of the total moths caught by center trap was lower than the average proportion caught
in perimeter traps at 5, 25, and 50 m (F = 2.79, P = 0.027). Differences were not detected between
the center and perimeter traps in the 100 and 250 m arrays (Table 2). Results indicate there is
substantial interference between traps placed less than 100m apart. Reduced trap capture in the
center trap relative to perimeter trap likely results from overlapping active spaces at low distances.
Additionally, data suggest the active distance of E. loftini pheromone traps may be greater than
100 m. Based on these results, pheromone traps should be placed at least 250 m
apart from in order to maximize trap performance. This experiment is being repeated in 2013 with
revised distances of 50, 100, 150, 225, and 300 m.
Figure 1: Hexagonal arrays of MRB pheromone traps.
= pheromone trap
X x = 5, 25, 50, 100, 250 meters
This research work is a portion of the Ph.D. program of study by Blake Wilson in the LSU
Department of Entomology. .
Table 1: Average daily trap capture of MRB pheromone
traps as affected by intertrap distance
Intertrap Distance (m)
MRB caught/trap/day
5 0.51 A
25 0.90 A
50 1.38 A
100 2.90 B
250 4.22 C
LS Means (± 1.1 [SE]). F= 16.9, df = 4,36, P<0.0001. Means which share a letter are not significantly different
(LSD, α=0.05).
Table 2: The proportion of total MRB catch caught by center traps versus
perimeter traps as affected by intertrap distance
Intertrap Distance (m)
Proportion of Total Array Catch
Central Trap Perimeter Traps
5 0.056* 0.157
25 0.044* 0.159
50 0.081* 0.156
100 0.102 0.150
250 0.163 0.142
LS Means. F= 2.79, df= 4, 293, P<0.0267.
*Central trap is significantly less than mean for perimeter traps (LSD, α=0.05).
FIELD AND FORAGE CROPS
Improved Chemical Control for the Mexican Rice Borer (Lepidoptera:Crambidae) in Sugarcane: Larval Exposure, a Novel Scouting Method,
and Efficacy of a Single Aerial Insecticide Application
B. E. WILSON,1,2 A. T. SHOWLER,3 T. E. REAGAN,1 AND J. M. BEUZELIN1
J. Econ. Entomol. 105(6): 1998Ð2006 (2012); DOI: http://dx.doi.org/10.1603/EC11271
ABSTRACT A three-treatment aerial application insecticide experiment was conducted in Þvecommercial sugarcane, Saccharum spp., Þelds in south Texas to evaluate the use of pheromone trapsfor improving chemical control of the Mexican rice borer, Eoreuma loftini (Dyar), in 2009 and 2010.A threshold of 20 moths/trap/wk was used to initiate monitoring for larval infestations. The percentageof stalks with larvae on plant surfaces was directly related to the number of moths trapped. Reductionsin borer injury and adult emergence were detected when a threshold of �5% of stalks with larvaepresent on plant surfaces was used to trigger insecticide applications. Novaluron provided superiorcontrol compared with �-cyßuthrin; novaluron treated plots were associated with a 14% increase insugar production. A greenhouse experiment investigating establishment and behavior of E. loftinilarvae on two phenological stages of stalkborer resistant, HoCP 85-845, and susceptible, HoCP 00-950,sugarcane cultivars determined that more than half of larvae on HoCP 00-950 and �25% on HoCP85-845 tunneled inside leaf mid-ribs within 1 d of eclosion, protected therein from biological andchemical control tactics. Exposure time of larvae averaged �1 wk for all treatments and was shorteston immature HoCP 00-950 and longest on mature HoCP 85-845. This study shows a short window ofvulnerability of E. loftini larvae to insecticide applications, and demonstrates the potential utility ofpheromone traps for improving insecticide intervention timing such that a single properly timedapplication may be all that is required.
KEY WORDS Eoreuma loftini, novaluron, chemical control, neonate, sugarcane
The Mexican rice borer, Eoreuma loftini (Dyar), is aninvasive crambid originating in Mexico, Þrst detectedin south Texas in 1980 (Johnson and Van Leerdam1981). Now the pest comprises �95% of the sugarcane,Saccharum spp., stalkborer population there (Legaspiet al. 1997) and causes �$10 million in annual revenuelosses (Legaspi et al. 1999). The insect has expandedinto the rice (Oryza sativaL.), production area of eastTexas (Browning et al. 1989, ReayÐJones et al. 2007a),and, recently, Louisiana (Hummel et al. 2010). By2035, E. loftini is predicted to infest all of LouisianaÕssugarcane areas with projected annual losses of $220million in sugarcane and $48 million in rice (ReayÐJones et al. 2008).
Insecticidal control of E. loftini has rarely improvedsugarcane yield (Johnson 1985, Meagher et al. 1994,ReayÐJones et al. 2005), and south Texas growers have
largely abandoned the tactic (Legaspi et al. 1997).However, a recently developed insect growth regu-lator (IGR), novaluron, suppresses E. loftini infesta-tions in sugarcane (Akbar et al. 2009). Modeled afterthe sugarcane borer, Diatraea saccharalis (F.), inter-vention threshold in Louisiana (Hensley 1971, Poseyet al. 2006), a threshold of �5% of stalks with E. loftinilarvae on plant surfaces indicates the need for aninsecticideapplication(Johnson1985). Scouting forE.loftini in sugarcane is labor intensive and identiÞcationof a relationship between adult population density andlarval infestations could improve early detection ofpopulation increases (Meagher et al. 1996). Phero-mone traps are effective at monitoring adult male E.loftini populations (Shaver et al. 1990, 1991; Reagan etal. 2001) and could be useful for determining insec-ticide application timing.
Chemical control of E. loftini is hindered by thelarvae boring into stalks and packing tunnels withprotective frass. Hence, insecticide applications targetearly instars that are exposed on plant surfaces (John-son 1985, Van Leerdam 1986, Meagher et al. 1994). E.loftini prefers to oviposit in folds that mostly occur ondry leaf material (Showler and Castro 2010b), pro-tected from insecticides and natural enemies. Aftereclosion, early instars disperse and feed on the green
Mention of trade names or commercial products in this publicationis solely for the purpose of providing speciÞc information and does notimply recommendation or endorsement by the US. Department ofAgriculture.
1 Department of Entomology, 404 Life Sciences Building, LSUCampus, Baton Rouge, LA 70803.
2 Corresponding author, e-mail: [email protected] Kika de la Garza Subtropical Agricultural Research Center,
USDAÐARS, 2413 E. Highway 83, Weslaco, TX 78596.
tissue of leaves and leaf sheaths before they enter thestalk (Van Leerdam 1986). Van Leerdam (1986) es-timated 10 d between eclosion and stalk entry, theaverage age of third instars reared at 29�C. Resistantcultivars might be able to extend the interventionwindow, hence increasing potential efÞcacy of insec-ticides. Because larvae are protected once they boreinto the stalk, the period of exposure while feeding onleaves and sheaths is the only time larvae are vulner-able to control tactics. Determination of duration oflarval vulnerability will have broad implications to E.loftini integrated pest management (IPM), including re-Þning the economic threshold (based on scouting forexposed larvae), developing cultivar-speciÞc interven-tion thresholds (Posey et al. 2006, White et al. 2008) andidentifyingresistancemechanisms.Theobjectivesof thisstudywere1) toassess theefÞcacyof an IGRapplicationundercommercialconditions, triggeredbyE. loftinipop-ulation monitoring with pheromone traps; 2) to deter-minethepestÕswindowof larvalexposureto insecticides;and 3) to assess effects of sugarcane cultivar and phe-nological stage on early instar feeding behavior and es-tablishment.
Materials and Methods
Aerial Insecticidal Control. A Þeld study was con-ducted in 2009 and 2010 using a randomized completeblock design, each of the Þve blocks (replications)being a 14Ð33 ha commercial sugarcane Þeld (varietyCP 72-1210) in Cameron and Hidalgo counties, TX.Each Þeld had three 4-ha plots for a nontreated con-trol, and threshold-triggered applications of novalu-ron (Diamond 0.83 EC; Makhteshim Agan of NorthAmerica Inc., Raleigh, NC) at 80 g (active ingredient[AI])/ha or �-cyßuthrin (Baythroid XL; Bayer Crop-Science, Research Triangle Park, NC) at 25 g (AI/ha).Adult E. loftini population densities were monitoredusing standard universal pheromone traps (Unitrap;Great Lakes IPM, Vestaburg, MI) (one per Þeld in2009, two per Þeld in 2010) baited with synthetic E.loftini female sex pheromone in a rubber septa lure(Luresept; Hercon Environmental, Emigsville, PA).Traps were attached to metal poles 1 m above the soilsurface �2 m inside the sugarcane Þelds, each trapcontaining an insecticidal strip (Vaportape II; HerconEnvironmental, Emigsville, PA) to maximize trap cap-ture (Shaver et al. 1991). Pheromone lures were re-placed every 2 wk and insecticidal strips were re-placed every 4 wk according to label instructions.
Traps were checked weekly from 15 July to 14October 2009 and from 1 June to 14 August 2010, andnumbers of captured male E. loftiniwere recorded. In2009, a threshold of �20 moths per trap per week wasdeveloped based on preliminary reports (Reagan et al.2001) and Þeld observations (T. E. Reagan, personalobservations). Trap catches exceeding this thresholdinitiated visual monitoring for larval infestations, byremoving all leaf sheaths and recording the presenceof larvae on 20 randomly selected stalks per Þeld.Larval monitoring was expanded in 2010 being con-ducted throughout thegrowing seasonbyexamination
of 10 stalks (1 June through 6 July) or 20 stalks (13 Julythrough 14 August) several rows in from trap locationsin all Þelds. Larval infestations exceeding the thresh-old of 5% of stalks with exposed larvae present on plantsurfaces triggered insecticide applications by a Þxedwing aircraft ßying at 233 km/h equipped with CP-03nozzles at 96 L/ha (�8 km/h wind) on the morningsof 21 August 2009 and 14 August 2010. Before harvest,15-stalk samples were collected on 28 October 2009and 8 November 2010 from two locations in each plotand the numbers of internodes, bored internodes, andmoth emergence holes were recorded. Plots were har-vested separately using conventional farm equipmentand the sugarcane was weighed. Tons of sugarcane perhectare (TCH) was calculated by dividing the totalweight of sugarcane (tons) harvested from each plotby the plot size (hectares). Sugarcane yield and qual-ity parameters were calculated by the Rio GrandeValley Sugar Growers laboratory with the core sam-pling method (Birkett 1975, 1979) including percent-age brix and percentage sucrose determined thoughdirect polarization. The ratio of sucrose to all otherdissolved solids, or juice purity, is expressed as a per-centage. Commercially recoverable sugar (CRS) wasrecorded for each core sample and extrapolated to oneton of cane that is expressed as pounds of sugar per tonof sugarcane. TSH was calculated by the following:TSH � (Mean CRS*TCH)/2000. Yield data were an-alyzed using generalized linear mixed models (ProcGLIMMIX; SAS Institute 2008) with Gaussian distri-butions. Means were converted to metric units afteranalysis. Yield data were only collected in 2010. Theunavailability of 2009 yield and quality data resultedfrom a rush by growers to harvest because of hardfreezes and rapid crop deterioration in December2009 and January 2010.
The numbers of internodes, bored internodes, andemergence holes from stalks were summed for each15-stalk sample to reduce effects of inter-stalk varia-tion. Data were analyzed with year, Þeld, Þeld � year,and Þeld � year � treatment as random effects. Theproportion of bored internodes was analyzed using ageneralized linear mixed model (Proc GLIMMIX; SASInstitute 2008) with a binomial distribution. Numbersof adult emergence holes were analyzed using a gen-eralized linear mixed model (Proc GLIMMIX; SASInstitute 2008) with a Poisson distribution. General-ized linear mixed models with appropriate distribu-tions were used (PROC GLIMMIX; SAS Institute2008) because proportion data (percentage of boredinternodes) and count data (number of emergenceholes) are not normally distributed. For all models, theKenwardÐRoger method (Kenward and Roger 1997)was used to compute denominator degrees of freedomfor the test of Þxed effects for all variables, and TukeyÕshonestly signiÞcant difference (HSD) test (Tukey1953) was used for mean separation. In addition, asimple linear regression between the numbers of maleE. loftini per pheromone trap per week and the per-centages of stalks infested with treatable larvae in 2010was conducted (Proc GLIMMIX; SAS Institute 2008).
December 2012 WILSON ET AL.: Eoreuma loftini MANAGEMENT IN SUGARCANE 1999
Early Instar Establishment and Behavior. A green-house study was conducted during the summer of 2010at the U.S. Department of AgricultureÐAgricultureResearch Services (USDAÐARS) Kika de la GarzaSubtropical Agricultural Research Center, Weslaco,TX, to investigate E. loftini early instar establishmentand feeding behavior on two phenological stages of anE. loftini resistant sugarcane cultivar, HoCP 85-845,and a susceptible cultivar, HoCP 00-950 (ReayÐJoneset al. 2005). Twenty-four sugarcane nodes of eachcultivar were obtained from Certis U.S.A. (BatonRouge, LA) sugarcane tissue cultures. All nodes wereplanted in mid May in 7.6-liter pots in Sunshine mix no.1 nursery potting soil (�75% sphagnum peat moss,perlite, dolomitic limestone, and gypsum; Sungro Hor-ticulture, Bellevue, WA). Plants were kept well wa-tered throughout their growth and 200 ml of PetersProfessional (ScottsÐSierra Horticulture ProductsCompany, Marysville, OH) water-soluble general pur-pose fertilizer was applied to the soil once plantsreached the two-leaf stage. Plants were arranged in acompletely randomized design as a 2 � 2 factorial,cultivar � phenological stage, with each of the fourtreatments replicated using 12 stalks.
The experiment was initiated when stalks had pro-duced six nodes (immature sugarcane) from 14 Junethrough 2 July, and from 30 July through 17 Augustwhen stalks had 12 nodes (mature sugarcane). Eggswere obtained from a laboratory colony reared fromE. loftini larvae collected from commercial sugarcaneÞelds in Hidalgo Co., TX, on artiÞcial diet (Martinezet al. 1988) at 25�C, 65% relative humidity (RH), anda photoperiod of 14:10 (L:D) h. After mating,E. loftinifemales deposited egg masses of 10Ð80 eggs on 1-cmwide paper strips. Before attaching strips using 2.5-cmpaper clips to the ventral side of leaves 15Ð25 cm fromthe stalk, eggs on each strip were counted. The paperstrips were removed 7 d later after eggs hatched andthe numbers of unhatched, presumably nonviable,eggs were counted under a microscope.
Over all treatments and replications, developmentand behavior of 277 early instars was examined bydirect observation and stalk dissection. On day 1 afteregg hatch, numerous entry holes in the mid-rib ofsugarcane leaves were observed indicating neonateshad bored into leaves with in 1 d of hatching ratherthan feeding in leaf sheaths as anticipated. The loca-tion of initial establishment was recorded as eithersheath feeding or mid-rib entry, and numbers andpositions of mid-rib entry holes were recorded. Allleaves and leaf sheaths on each plant were examineddaily over 14 consecutive days for the presence ofearly instar E. loftini, and the location of feeding sites(mid-rib or sheath), dispersal distance from oviposi-tion sites, and time to stalk entry were recorded. Thepercentage of larvae that became established on eachstalk was based on the number of larvae observedfeeding on or in leaves and leaf sheaths out of thenumber of hatched eggs. Dispersal of early instars,expressed as number of internodes traversed fromoviposition sites, was recorded for all established lar-vae. Early instars feeding within the leaf sheaths were
monitored daily by checking between the stalk andleaf sheath for the presence of larvae. Daily examina-tion of each sheath was conducted until entry holeswere observed or larvae were recorded as dead orvanished. Survival to stalk entry and duration of leafsheath feeding (time from eclosion to mid-rib or stalkentry) were recorded. After allowing 4 wk for devel-opment, stalks were dissected and the numbers andlocations of entry holes and live larvae and pupae wererecorded. The proportion of larvae that became es-tablishedon the stalk and theproportionsentering leafmid-ribs and surviving to stalk entry were not trans-formed and were analyzed using generalized linearmixed models (Proc GLIMMIX; SAS Institute 2008)with binomial distributions. A separate analysis thatexcluded larvae that had entered into the mid-rib com-pared effects of treatments on duration of leaf sheathfeeding. A linear mixed model (Proc GLIMMIX; SASInstitute 2008) was used to analyze data on the durationof exposure, duration of leaf-sheath feeding, and larvaldispersal.
Results
Aerial Insecticidal Control. Pheromone trap cap-tures in both 2009 and 2010 peaked in late August (Fig.1). Larval infestations ranged from 5 to 32% with amean of 13.8 � 1.8% of stalks with treatable larvaepresent on plant surfaces on 20 August 2009, a daybefore insecticide applications. A steady decline in themean number E. loftini per trap per week occurred inSeptember and October after the 21 August 2009 in-secticide application (Fig. 1). On 14 August 2010 larvalinfestations ranged from 5 to 22.5% with a mean of11.3 � 1.5% of stalks with larvae exposed on plantsurfaces. Weekly monitoring of larval infestations in2010 allowed for determination of the relationshipbetween adult population density and larval infesta-tion (Fig. 2). Linear regression revealed a relationship(F� 280.7; df � 1, 114; P� 0.0001;R2 � 0.71) betweenpheromone trap catches and larval infestation that canbe summarized by the equation, y � 0.213x Ð 0.038,where x is the number of E. loftini per trap per weekandy is the percentage of stalks infested with treatablelarvae feeding on plant surfaces.
The probability of occurrence of a bored internodewas reduced compared with nontreated controls by anaverage of 40.3 and 60.2% over both years in �-cyßu-thrin and novaluron treated plots, respectively (F �11.41; df � 2, 18.2; P � 0.0006) (Fig. 3A). The meannumbers of emergence holes per stalk were 37.4 and58.4% lower than nontreated controls over both yearsfor �-cyßuthrin and novaluron treated plots, respec-tively (F � 4.65; df � 2, 17.2; P � 0.0244) (Fig. 3B).
Yield data from 2010 indicate that reduced injury innovaluron treated plots was associated with improvedjuice purity by 1%, percentage sucrose by 3.5%, per-centage brix by 3%, sugar per metric ton of sugarcaneby 5.3%, metric tons of sugarcane per hectare by 8.8%,and recoverable sugar (metric tons of sugar per hect-are) by 14% (Table 1) compared with untreated con-trols. �-cyßuthrin treated plots were only different
2000 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 6
from controls in terms of sugar yield per metric ton ofsugarcane (2.6% increase).Early Instar Establishment and Behavior. On the
Þrst day after egg hatch, numerous entry holes in themid-ribsof sugarcane leaveswereobserved, indicatingthat 24.1 to 67.5% of early instars had bored into leaveswithin 1 d of hatching (Table 2). The mean percentageof larvae surviving to stalk entry ranged from 27.4 to72.4% among treatments, and mean duration of expo-sure ranged from 3.5 to 6.4 d (Table 2).
Over both phenological stages of sugarcane, the per-centage of early instars that became established on the
plant was 40% greater on susceptible cultivar HoCP 00-950 than on resistant HoCP 85-845 (Table 2). The per-centage of established larvae that bored into the leafmid-rib was twice as high on HoCP 00-950 as on HoCP85-845 (Table 2). Average dispersal distance (numbersof internodes from oviposition sites) was 19% greater onHoCP 85-845 than on HoCP 00-950 (Table 2). Durationof exposure of all established larvae was 40% longer onHoCP 85-845 than HoCP 00-950. Duration of leaf sheathfeedingwas14.7%longer inHoCP85-845comparedwithHoCP 00-950 when considering only established larvaefeeding in leaf sheaths (Table 2).
Fig. 1. Pheromone trap monitoring of E. loftini in Hidalgo and Cameron Counties, TX. (A) Average no. of E. loftini pertrap per week (�SE) from 15 July to 14 October 2009; (B) Average no. of E. loftini per trap per week (�SE) from 1 Juneto 10 August 2010.
Fig. 2. Relationship between adult population densities (number of E. loftini per trap per week) and larval infestation(percent of stalks infested with treatable larvae feeding in leaf sheaths), 2010.
December 2012 WILSON ET AL.: Eoreuma loftini MANAGEMENT IN SUGARCANE 2001
The percentage of larvae to become establishedfeeding in leaves and leaf sheaths was 60% greater onmature than on immature plants, and the percentageof established larvae surviving to stalk entry was 90%greater on immature than on mature sugarcane. Av-erage dispersal distance was 30% greater on immaturethan on mature sugarcane (Table 2). All dispersal onimmature sugarcane was toward the top of the stalkwhile 21% of larvae moved down from oviposition siteson mature sugarcane. Duration of exposure was 20%greater on mature plants than immature, and an in-teraction effect was detected between cultivar andphenological stage for the percentage of early instarsentering the mid-rib and the percentage of establishedlarvae surviving to stalk entry (Table 2). ImmatureHoCP 00-950 had the greatest percentage of larvae
entering the mid-rib within 1 d and a mean durationof exposure of only 3.5 d (Table 2). Duration of larvalexposure was longest, 6.4 d, on mature HoCP 85-845.
Discussion
Use of pheromone traps to assist scouting for E.loftini in sugarcane demonstrates potential to reducescouting effort and improve chemical control. A scout-ing thresholdbasedonpheromone trapcapturescouldenhance scouting efÞciency by focusing larval moni-toring at the most appropriate times when adult pop-ulation densities are high. When a threshold of 20 E.loftini per trap per week was used (Reagan et al. 2001,T.E.Reagan,personalobservations)onlyone instanceof larval scouting was necessary in 2009. Weekly larvalscouting from June to mid-August in 2010 revealed astrong positive relationship between numbers of E.loftini per trap per week and the percentage of stalksinfested with treatable larvae on plant surfaces. Linearregression analysis indicated a trap catch of 23.6 E.loftini per trap per week corresponds to the treatmentthreshold of 5% of stalks infested with treatable larvae.These results indicate an action threshold of 20 E.loftini per trap per week is appropriate to initiatescouting and verify larval infestations. However, fur-ther evaluation of the relationship between larval in-festations and pheromone trap captures under a va-riety of environmental conditions may be neededbefore this approach is extensively used. Therefore,pheromone trap assisted scouting could potentially befurther developed for use on a broad commercial scaleto increase monitoring efÞciency in Texas and Loui-siana. LouisianaÕs sugarcane industry is heavily depen-dent on consultant scouting for D. saccharalis infes-tations, and the infrastructure is in place to usepheromone trap assisted scouting when E. loftini be-comes established as a major economic pest in Loui-siana sugarcane (ReayÐJones et al. 2008, Hummel et al.2010).
When timed in accordance with our threshold, asingle insecticide application reduced E. loftini injuryand adult emergence in both 2009 and 2010. The su-perior control of novaluron in comparison to �-cyßu-thrin is likely the result of both residual and trans-laminar activity (Ishaaya et al. 2002, 2003), andconservation of beneÞcial arthropods (Beuzelin et al.2010). Novaluron has substantial residual and trans-laminar activity remaining effective for up to 5 wk
Fig. 3. E. loftini injury, sugarcane aerial insecticide ap-plication experiment in Cameron and Hidalgo Counties, TX,2009 and 2010. (A) LS mean (�SE) percentage of E. loftinibored internodes; (B) LS mean (�SE) no. moth emergenceholes per stalk. Bars within each chart followed by the sameletter are not signiÞcantly different (P� 0.05; TukeyÕs HSD).
Table 1. Sugar yield and quality (LS means � SE) as affected by insecticide treatments, Cameron and Hidalgo Counties, TX, 2010
PurityPOL
(% sucrose)% brix
Sugar (kg/metricton of sugarcane)
Cane(metric ton/ha)
Sugar(metric ton/ha)
Novaluron 85.3 � 0.4a 14.5 � 0.17a 17.0 � 0.2a 104.07 � 1.85a 70.1 � 4.2a 7.29 � 0.48aBaythroid 85.0 � 0.4ab 14.2 � 0.18b 16.7 � 0.2b 101.47 � 1.85b 58.7 � 4.2b 5.97 � 0.48bControl 84.4 � 0.4b 14.0 � 0.17b 16.5 � 0.2b 98.87 � 1.85c 64.4 � 4.2ab 6.39 � 0.48abF 4.15a 13.94a 7.47a 16.03a 5.60b 6.78b
P � F 0.018 �0.0001 0.0009 �0.0001 0.03 0.019
Means in same column that share the same letter are not signiÞcantly different (P � 0.05; TukeyÕs HSD).a df � 2, 124.b df � 2, 8.
2002 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 6
depending on environmental conditions (Ishaaya etal. 2002, 2003; Cutler et al. 2005). �-cyßuthrin has alonger residual activity, relative to other pyrethroids(Athanassiou et al. 2004), but its residual activity isnegatively correlated with temperature and toxicity isgreatly reduced at temperatures exceeding 25�C (Ar-thur 1999). The negative relationship between pyre-throid residual activity and temperature (Toth andSparks 1990) might be an important factor limitingpyrethroidefÞcacy in southTexaswhere summer tem-peratures regularly exceed 35�C. Novaluron and otherIGRs are generally less toxic to nontarget arthropodsthan pyrethroid insecticides, better preserving naturalpest suppression (Reagan and Posey 2001, Beuzelin etal. 2010). Reduced predation in �-cyßuthrin treatedplots might have contributed to weaker control rela-tive to novaluron treated plots.
Previous studies have shown that chemical controlof E. loftini is inadequate to improve sugarcane yieldeven after multiple insecticide applications (Johnson1985, Meagher et al. 1994, Legaspi et al. 1997, ReayÐJones et al. 2005). However, our study indicates thatmuch of the difÞculty might have been in part becauseof relatively poor timing of insecticide applications.The economics of E. loftini management using insec-ticides could be improved by reduction of multipleapplications that are inefÞcient, and relying more ona single well-timed insecticide application that in-creases yield. While yield data were only collected for1 yr, the reduced yield loss detected in 2010 is con-sistent with the 2 yr of injury data (proportion ofbored internodes) presented. The relationship be-tween borer injury and yield is well established (Met-calfe 1969, White and Hensley 1987, Legaspi et al.1999, White et al. 2008, ReayÐJones et al. 2008). Yield
and quality parameters such as sugar per hectare, juicepurity, and sucrose content have been documented asbeing inversely related to percentage of E. loftinibored internodes (Legaspi et al. 1999). We suggestthat past failures to detect improved yields despitechemically induced reductions in percentages ofbored internodes (Johnson 1985, Meagher et al. 1994,Legaspi et al. 1999, ReayÐJones et al. 2005) resultedfrom high variability in sugarcane yield studies, par-ticularly involving small plot tests. Our experimentwas the Þrst to adequately replicate larger areas (4 haper treatment plot with Þve replications) and likelyprovides a more accurate assessment of insecticideapplication effects on sugar yield and quality undercommercial conditions. A single application of novalu-ron enhanced subsequent sugar yield by 14% com-pared with controls in 2010, and based on the currentprice of raw sugar, $766.77/metric ton (U.S. Dep. Ag-ric.ÐERS 2011), the novaluron treatment is expectedto increase revenue by $690.09/ha, representing theÞrst report of insecticidal E. loftini control resulting inincreased sugar yield and quality. Based on an aerialapplication cost with 95 L/ha of $37.50/ha (Salassi andDeliberto 2009) and the retail cost of novaluron of$30.00/ha the net economic beneÞt of the applicationwas $622.59/ha. However, because only 1 yr of yielddata were collected in this study, insecticide effects onyield will require further evaluation.
The importance of application timing and develop-ment of management tactics that target early instars isfurther supported by greenhouse research that sug-gests the duration of larval exposure on plant surfacesis substantially shorter than previously estimated (VanLeerdam 1986, Ring et al. 1991). Because larvae areprotected once they bore into the stalk, the period of
Table 2. E. loftini neonate establishment and behavior on two phenological growth stages of sugarcane cultivars HoCP 84-845(resistant) and HoCP 00-950 (susceptible), Weslaco, TX, 2010
Eclosed larvaeestablished (%)
Established larvaeentering mid-ribwithin 1 d (%)
Established larvaesurviving to stalk
entry (%)
Dispersal distance(nodes from
oviposition site)
Duration of exposure (d)
All establishedlarvae
Established larvaein leaf sheaths
Growth stageImmature 16.02 44.84 64.17 1.46 4.68 6.37Mature 26.15 37.58 33.89 1.15 5.90 7.79F 15.43a 0.91a 16.77a 1.81b 4.23c 21.03d
P � F 0.0003 0.3447 0.0002 0.1815 0.0417 �0.0001Cultivar
HoCP 85-845 17.63 28.30 49.88 1.42 6.18 7.56HoCP 00-950 23.99 55.36 47.98 1.19 4.39 6.59F 5.08a 13.27a 0.06a 0.99b 9.13c 9.73d
P � F 0.0176 0.0007 0.8047 0.3214 0.0038 0.0025Growth stage � cultivar
ImmatureHoCP 85-845 14.08 24.14 72.41 1.76 5.95 7.12HoCP 00-950 18.18 67.50 55.00 1.16 3.40 5.62
MatureHoCP 85-845 21.86 32.88 27.40 1.08 6.41 8.00HoCP 00-950 30.95 42.54 41.04 1.23 5.38 7.57
F 0.28a 5.42a 5.08a 2.65b 1.65c 3.01d
P � F 0.5990 0.0246 0.0293 0.1073 0.2006 0.0864
a df � 1, 44.b df � 1, 159; considers all larvae.c df � 1, 127; considers all larvae surviving until stalk entry.d df � 1, 85; considers leaf sheath-feeding larvae that survived until stalk entry.
December 2012 WILSON ET AL.: Eoreuma loftini MANAGEMENT IN SUGARCANE 2003
exposure while feeding on leaves and sheaths is theonly time larvae are vulnerable to control tactics. De-termination of duration of larval vulnerability will havebroad implications to E. loftini IPM, including reÞningthe economic threshold (based on scouting for exposedlarvae),developingcultivar-speciÞcinterventionthresh-olds (Posey et al. 2006, White et al. 2008) and identifyinghost plant resistance mechanisms.
The rapid entry of most E. loftini larvae into sus-ceptible sugarcane (1 d) is substantially shorter thanthe 10 d reported by Van Leerdam (1986). In ourstudy, early instar entry into the mid-ribs was re-corded, and the appearance of entry holes in the stalkssuggests these larvae also successfully entered thestalk with limited exposure on plant surfaces. Similarto E. loftini, the unsatisfactory performance of insec-ticides against Eldana saccharina (Walker) in SouthAfrica (Heathcote 1984) might be because �5% oflarvae bore into sugarcane plant surfaces within 1 d(Leslie 1993). Our research shows this behavior is rel-atively more frequent in E. loftini, and is likely an im-portant factor limiting the success of chemical control.
Differences in larval behavior between cultivarssuggest that resistant varieties impede larval establish-ment with the potential to improve efÞcacy of othercontrol tactics. A greater percentage of larvae to be-come established feeding in leaves or leaf sheaths onsusceptible HoCP 00-950 than on the resistant HoCP85-845 occurred because more larvae bored into theplant within 1 d. Longer larval exposure on the resis-tant cultivar might be partly because of greater dis-persal on the resistant cultivar than on the susceptiblecultivar. The lack of differences in the percentage ofestablished larvae to enter the stalk between cultivarssuggests the mechanism of resistance such as leafsheath appression (Coburn and Hensley 1972) oc-curred before stalk entry.
Less space available on young sugarcane, particu-larly the lesser amount of folded leaf tissue, might havelimited larval establishment (Showler and Castro2010b). Once established, larval survival to stalk entryon immature sugarcane was nearly twice as great asthat on mature sugarcane indicating young internodesare more susceptible to borer entry. Although morelarvae became established feeding on the leaves andsheaths of mature sugarcane plants, proportionatelyfewer successfully entered the stalk relative to imma-ture sugarcane possibly because immature sugarcaneplants have greater nutritional value than mature sug-arcane plants (ReayÐJones et al. 2007b). Further, thelonger exposure on mature sugarcane plants suggeststhat physiological factors, such as increased rind hard-ness (Martin et al. 1975), of mature sugarcane impedesstalk boring (Van Leerdam 1986, Ring et al. 1991).Similarly, D. saccharalis establishment on corn plantsurfaces infested at later growth stages is greater thanon younger corn attributable to decreased leaf sheathappression as plants age, while larval stalk entry wasgreater on younger corn (Flynn et al. 1984). Host plantcharacteristics unfavorable to larval establishment areimportant components of host plant resistance tostalkborers (Mathes and Charpentier 1969), and re-
sistance mechanisms that prolong larval exposure out-side the stalk enhance the efÞcacy of other controltactics including insecticide applications and biolog-ical control. Research has consistently shown that thegreatest suppression of sugarcane stalkborer infesta-tions is achieved when insecticide applications areused in conjunction with host plant resistance (Bessinet al. 1990b, ReayÐJones et al. 2005, Posey et al. 2006).Rapid early instar entry into the mid-rib suggests thatE. loftini larvae are only brießy exposed to foliar ap-plied contact insecticides. Hence, longer residual ac-tivity of insecticides will likely contribute to improvedcontrol. The residual and translaminar activity of no-valuron (Ishaaya et al. 2002, 2003) is likely responsiblefor the superior control observed in our Þeld study.
Elements of potential control strategies highlightedby this research include the use of pheromone traps toassist scouting and substantially improve applicationtiming, increased residual activity of insecticides, andresistant cultivars that impede larval entry into thestalk. In Louisiana E. loftini is expected to inßict sub-stantial revenue losses (ReayÐJones et al. 2008), andthe need to develop management strategies is becom-ing urgent. In addition to reducing injury and increas-ing yield, control tactics that reduce adult emergencecould aid in managing area-wide populations (Bessinet al. 1990a) and slow the expansion of this invasivepest. Our Þndings on a new monitoring method, anintervention threshold, insecticide efÞcacy, and earlyinstar behavior relative to varietal resistance and sug-arcane plant phenology all contribute, in addition toproviding suitable irrigation and avoidance of soil sa-linity (ReayÐJones et al. 2005, Showler and Castro2010a), toward the advancement of increasingly ef-fective E. loftini IPM.
Acknowledgments
The authors express appreciation to Jaime Cavazos andVeronica Abrigo (USDAÐARS Kika de la Garza, SubtropicalAgricultural Research Center, Weslaco, TX), Sebe Brown(LSU AgCenter, Baton Rouge, LA), and Waseem Akbar(formerly LSU AgCenter) for technical assistance. Addi-tional thanks are expressed to Jim Trolinger, Tony Prado, andRio Grande Valley Sugar Growers Inc. for continuous sup-port and collection of yield and quality data. We also thankcommercial sugarcane growers with S.R.S. farms and Har-Vest for their cooperation. Appreciation is expressed to JeffFlynn of Certis U.S.A. for providing sugarcane cultivars. Grat-itude is expressed to David Blouin (LSU AgCenter) for sta-tistical consulting. This work was supported in part by grantsfrom the USDA (National Institute of Food and Agriculture)Crops at Risk Program (2008-51100-04415), the EPA Strate-gic Agricultural Initiative Program (0348-0046), and theAmerican Sugar Cane League. This paper is approved by theDirector of the Louisiana Agricultural Experiment Station asmanuscript no. 2012-234-7040.
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Received 12 August 2011; accepted 15 August 2012.
2006 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 6
Oviposition and larval development of a stem borer,Eoreuma loftini, on rice and non-crop grass hostsJ.M. Beuzelin1*, L.T. Wilson2, A.T. Showler3, A. M�esz�aros1, B.E. Wilson1, M.O. Way2 &T.E. Reagan11Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA, 2Texas A&M
AgriLife Research and Extension Center, Texas A&MUniversity, Beaumont, TX 77713, USA, and 3Kika de la Garza
Subtropical Agricultural Research Center, USDA-ARS,Weslaco, TX 78596, USA
Accepted: 7 November 2012
Key words: oviposition preference, larval developmental performance, free amino acids,
Lepidoptera, Crambidae,Oryza sativa, Poaceae
Abstract A greenhouse study compared oviposition preference and larval development duration of a stem
borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), on rice, Oryza sativa L. cv Cocodrie (Poa-
ceae), and four primary non-crop hosts of Texas Gulf Coast rice agroecosystems. Rice and two peren-
nials, johnsongrass, Sorghum halepense (L.) Pers., and vaseygrass, Paspalum urvillei Steud. (both
Poaceae), were assessed at three phenological stages. Two spring annuals, brome, Bromus spec., and
ryegrass, Lolium spec. (both Poaceae), were assessed at two phenological stages. Phenological stages
represented the diversity of plant development stages E. loftini may encounter. Plant fresh biomass,
dry biomass, and sum of tiller heights were used as measures of plant availability. Accounting for
plant availability, rice was preferred over non-crop hosts, and intermediate and older plants were pre-
ferred over young plants. Johnsongrass and vaseygrass were 32–60% as preferred as rice when consid-
ering the most preferred phenological stages of each host. Brome and ryegrass received few or no
eggs, respectively. Eoreuma loftini larval development (in degree days above developmental threshold
temperatures) was fastest on rice and slowest on johnsongrass and vaseygrass. Development duration
was only retarded by plant stage on young rice plants. Foliar and stem free amino acid concentrations
were determined to help provide insights on the mechanisms of E. loftini oviposition preference and
developmental performance.
Introduction
Eoreuma loftini (Dyar) (Lepidoptera: Crambidae) is a stem
borer indigenous to Mexico that has become an invasive
pest of grass crops in the Gulf Coast regions of Texas and
Louisiana (Hummel et al., 2010). In addition to sugar-
cane, Saccharum spp., and rice, Oryza sativa L., E. loftini
infests a wide range of non-crop graminoids (Van
Zwaluwenburg, 1926; Beuzelin et al., 2011a,b; Showler
et al., 2011). Periodic sampling over 2 years showed that
non-crop grasses in southeast Texas rice production areas
host E. loftini at densities between 0.2 and 5.7 immatures
per m2 (Beuzelin et al., 2011a). Primary hosts were the
perennials johnsongrass, Sorghum halepense (L.) Pers., and
vaseygrass, Paspalum urvillei Steud., as well as the annuals
ryegrass, Lolium spp., and brome, Bromus spp. (all Poa-
ceae) (Beuzelin et al., 2011a). Because non-crop grasses
increase host availability in the ecosystem, they play a role
in E. loftini population dynamics and may contribute to
economically damaging populations in host crops.
However, the extent to which non-crop hosts increase
E. loftini populations remains poorly understood.
Host-specific development, survival, fecundity, and
preference are key factors influencing the relative contri-
bution of multiple host plants to herbivore populations.
Meagher et al. (1996) observed variations in E. loftini
immature development time and pupal weight among
sugarcane genotypes, but differences in oviposition were
not detected. Reay-Jones et al. (2003, 2005) did not find
differences in E. loftini larval survival among sugarcane
cultivars grown in Louisiana and Texas. Subsequent stud-
ies involving sugarcane showed that cultivar HoCP 85–845is 17–37% less preferred for oviposition than LCP 85–384
*Correspondence and current address: Julien Beuzelin, Dean LeeResearch Station, 8105 TomBowmanDr., Alexandria, LA 71302,
USA. E-mail: [email protected]
© 2013 The Netherlands Entomological Society Entomologia Experimentalis et Applicata 146: 332–346, 2013
332 Entomologia Experimentalis et Applicata© 2013 The Netherlands Entomological Society
DOI: 10.1111/eea.12031
based on numbers of egg clusters and eggs per plant, and
eggs per egg cluster (Reay-Jones et al., 2007a). Reay-Jones
et al. (2007a) and Showler & Castro (2010a) showed that
E. loftini also prefers drought-stressed sugarcane for
oviposition. Increased preference was associated with a
greater abundance of oviposition substrate (folded dry leaf
material) and increased levels of free amino acids (FAAs).
Showler et al. (2011) studied oviposition and injury on
five weedy grasses, including johnsongrass and vaseygrass.
Johnsongrass received more E. loftini eggs than vaseygrass
on a per plant basis. Johnsongrass also exhibited more
adult exit holes than vaseygrass, indicating differences in
E. loftini immature performance (Showler et al., 2011).
Previous studies show that E. loftini oviposition prefer-
ence and immature performance are affected by host plant
species and genotype, stress, and phenology (Meagher
et al., 1996; Reay-Jones et al., 2007a; Showler et al., 2011).
To better understand the role of non-crop hosts in rice
agroecosystems of the Gulf Coast, a study was conducted
to determine E. loftini oviposition preference and larval
development duration on rice and four primary non-crop
hosts.
Materials and methods
Greenhouse experiment
A greenhouse experiment was conducted at the Texas
A&M AgriLife Research and Extension Center at Beau-
mont (Beaumont, TX, USA; 30.068°N, 94.292°W) during
the summer of 2009. Rice (cv. Cocodrie), johnsongrass
and vaseygrass (perennial grasses), and brome and ryegrass
(annual grasses) were studied. Rice and johnsongrass seeds
were obtained from the Louisiana State University Agri-
cultural Center Rice Research Station (Rayne, LA, USA)
and Azlin Seed Service (Leland, MS, USA), respectively.
Other seeds were obtained from on-farm collections
in Chambers and Jefferson Counties, TX, USA, during
2007 (brome, ryegrass) and 2008 (vaseygrass). Thirteen
plant 9 stage combinations, hereafter referred to as host
treatments, were studied. Rice and the perennials were
evaluated at three phenological stages. The annuals were
evaluated at two phenological stages. Phenological stages
were selected to represent the diversity of plant develop-
ment stages encountered by E. loftini in Gulf Coast
rice agroecosystems. At the time of E. loftini oviposition
assessment, young rice was between the late tillering and
panicle differentiation stages, and the young non-crop
grasses were in vegetative growth (Table 1). Intermediate
rice was early in the panicle exertion stage, while the oldest
tillers of intermediate johnsongrass and vaseygrass exhib-
ited emerging inflorescences and mature seed heads,
respectively. Intermediate brome and ryegrass were in a
vegetative stage (Table 1). Older rice plants exhibited
maturing panicles in the hard dough stage, whereas older
johnsongrass and vaseygrass hadmature seed heads.
Plantings were scheduled to produce the various pheno-
logical stages simultaneously, with the earliest planting ini-
tiated on 14 April 2009 for vaseygrass. Planting occurred
in 3.8-l pots filled with sterilized soil provided by the Loui-
siana State University Central Research Station greenhouse
services (2:1:1 soil:sand:peat moss mixture). For each host
treatment, 25–30 pots were used. Final plant density was
reduced to one plant per pot, with the exception of two
young annual grasses per pot. For rice, three seeds were
planted directly in each pot, and 2–3 weeks after seedling
emergence, all but one plant were removed. For non-crop
grasses, seeds were soaked in a gibberellic acid solution
(300 p.p.m., N-Large; Stoller Enterprises, Houston, TX,
USA) for 24–36 h at 20 °C, and then planted in
60 9 30 9 5 cm plastic flats. On 7–14 days after emer-
gence, four seedlings were transplanted into each pot.
Three weeks after transplant, all but one plant were
removed.
Plants were fertilized 7–14 days after seedling emer-
gence (rice) or at transplanting (non-crop grasses) with
300 mg of urea and 250 ml of Miracle-Gro Water Soluble
All Purpose Plant Food (24-8-16 N-P-K; Scotts Company,
Marysville, OH, USA) solution at 3.7 g l�1 per pot. The
first plantings of rice, johnsongrass, and vaseygrass were
fertilized a second time on 16 June with 300 mg of urea
and 80 ml of Miracle-Gro solution per pot. On 21 July,
the first and second plantings of rice, johnsongrass, and
vaseygrass, as well as the first plantings of brome and
ryegrass, were fertilized with 300 mg of urea and 80 ml of
Miracle-Gro solution per pot. Plants were provided with
0.5 l of water per pot every other day.
Thirteen 1.3 9 1.3 9 1.8 m cages were constructed
from PVC pipes (2.13 cm outside diameter) and covered
with white polyester, 0.25-mm mesh netting. Cages were
arranged in two adjacent rows of six and seven cages each,
perpendicular to the cooling panel of the greenhouse.
Temperatures were recorded every 15 min using two
HOBO U10 data loggers (Onset Computer Corporation,
Pocasset, MA, USA). The cages closest and farthest from
the greenhouse cooling panel each had one data logger
located 1.2 m above the floor. Temperatures in each of the
13 cages were estimated using equation (1):
Ti ¼ 6� i
6� T0 þ i
6� T6; ð1Þ
where Ti = the temperature in a cage at the i-th position,
with i ∈ {0,1,2,3,4,5,6} and i = 0 for the cages closest to
the cooling panel (two cages per position at positions 0–5,
Oviposition and larval development of Eoreuma loftini 333
one cage at position 6), T0 = the temperature recorded in
the cage closest to the cooling panel, and T6 = the temper-
ature recorded in the cage farthest from the cooling panel.
One pot of each host treatment was placed into each cage
at a random location 1 week before oviposition was
assessed.
Insects used in the experiments were obtained from a
colony maintained at the USDA-ARS Kika de la Garza
Subtropical Agricultural Research Center in Weslaco, TX,
USA (27.157°N, 97.964°W). The E. loftini colony was
established from larvae collected in commercial sugarcane
fields nearWeslaco, during the spring of 2009. Insects were
reared on artificial diet (Martinez et al., 1988) at 25 °C,65% r.h., and L14:D10 photoperiod. Pupae were separated
by sex, and shipped overnight to the Texas A&M AgriLife
Research and Extension Center at Beaumont. Pupae were
kept in the greenhouse, and upon adult eclosion (<24 h),
10 females and 5–10 males were confined together in
473-ml paper containers (Neptune Paper Products,
Newark, NJ, USA) for 24 h to allow for mating. Adults
were released between 17:00 and 19:00 hours from one
paper container placed at the center of each cage. Eoreuma
loftini releases occurred between 14 and 26 August. After
allowing for three full nights of egg laying, each plant was
visually inspected for eggs. The number of oviposition
events (i.e., egg clusters and single eggs laid � 5 mm from
one another) and eggs per oviposition event were deter-
mined using a magnifying lens. With the exception of two
cages where a small proportion of the eggs were recovered
on the mesh cloth, E. loftini oviposition exclusively
occurred on plant material. Eggs laid on the mesh cloth
were destroyed and not included in data analyses.
After oviposition data collection, plants were main-
tained in cages for 5–6 weeks and then dissected for collec-
tion of E. loftini larvae and pupae (18 September–4October). Recovered pupae were kept in the greenhouse in
30-ml plastic cups until adult eclosion. Recovered larvae
were reared on artificial diet (Martinez et al., 1988) in
plastic cups maintained in the greenhouse until pupation
and adult eclosion. Adult eclosion was recorded daily until
the experiment was ended on 24November.
Plant measurements
The numbers of tillers, numbers of green and dry leaves,
and tiller heights from the soil surface to the tip of the tall-
est leaf were recorded for each plant in each cage immedi-
ately prior to moth release. From five representative plants
not used for oviposition assessment, numbers of tillers, til-
ler heights, and plant fresh biomasses were recorded for
each host treatment. Dry biomass was recorded after
5 days in an oven at 75 °C. For each host treatment, sim-
ple linear regressions (Proc REG; SAS Institute, 2008) were
conducted using the sum of tiller heights by plant as the
explanatory variable, and plant fresh and dry biomasses as
response variables. Parameters from these regressions were
used to estimate biomasses for each plant in each cage.
During plant dissection, numbers of tillers, tiller heights,
and tiller diameters (as measured ca. 1 cm below the first
visible node, or ca. 3 cm above the cut if the nodal position
was not determined) were recorded for each plant in each
cage. One-way ANOVAs were used to compare plant char-
acteristics as affected by host treatment and least squares
means (LS means) were separated using the Tukey adjust-
ment (a = 0.05) (Proc MIXED; SAS Institute, 2008).
‘Cage’ was included in the ANOVA models as a random
effect. In addition, multiple contrasts compared selected
groups of host treatments (Proc MIXED) with P-values
adjusted using the step-down Bonferroni method to con-
trol familywise error rates (Proc MULTTEST; SAS Insti-
tute, 2008).
Free amino acid analyses
Concurrently to oviposition assessment, samples of each
host treatment collected from five (rice, johnsongrass,
vaseygrass) or four (brome, ryegrass) plants not used for
oviposition were used for FAA analyses. Whole-plant sam-
ples, excluding roots, were collected from young annual
grasses. Leaf and stem samples were collected from other
plants. For leaves, a composite sample of the midsection of
at least two green leaf blades was collected from each plant.
For stems, a composite sample of the midsection of one or
more culms (stems with leaf sheaths removed) was col-
lected from each plant. Samples were stored on dry ice
upon collection, before being placed in a �80 °C freezer.
Each sample (0.5–1 g fresh biomass) was ground in amor-
tar with liquid N and subsequently homogenized with
0.1 N HCl (1 ml per 0.1 g of sample) using a Virtishear
homogenizer (Virtis, Gardiner, NY, USA) for 30–60 s.
After allowing homogenized samples to settle for 1–2 min,
the clear fraction between the floating and precipitating
debris was pipetted into 1.5-ml Eppendorf tubes and
stored at �80 °C. Each sample was processed using the
method of Showler & Castro (2010a) with an Agilent 1100
Series HPLC system (Agilent Technologies, Atlanta, GA,
USA). Concentrations of nine derivatized essential FAAs
and eight non-essential FAAs were determined. Essential
FAAs are not synthesized by insects and their absence in
food sources can prevent development (Chapman, 1998).
Essential FAAs include arginine, histidine, isoleucine,
leucine, lysine, methionine, phenylalanine, threonine, and
valine. The 10th essential FAA, tryptophan, was not
detected using our instrumentation. Non-essential FAAs
include alanine, aspartate, cystine, glutamate, glycine, pro-
line, serine, and tyrosine. ANOVAs (Proc MIXED) were
334 Beuzelin et al.
used to compare concentrations of each FAA, in pmol of
FAA per ll of juice, in leaves and stems as affected by host
treatment. Fixed effects for the ANOVAmodels were ‘host
treatment’ and ‘host tissue (host treatment)’. The effect of
individual plants – i.e., ‘plant(host treatment)’ – was
included as a random effect. Least squares means were sep-
arated using the Tukey-Kramer adjustment (a = 0.05). In
addition, a principal component analysis on standardized
averages of FAA concentrations in leaves and stems for
each host treatment was performed to assist in visualizing
potential associations between combinations of FAAs and
host treatments (Proc PRINCOMP; SAS Institute, 2008).
Oviposition preference estimation
Oviposition preference is a departure from random plant
host selection when multiple plant hosts are simulta-
neously available for egg laying. A preference coefficient
(Wilson & Gutierrez, 1980; Murphy et al., 1991; Reay-
Jones et al., 2007a) for a host plant, which accounts for
plant availability, can be estimated using equation (2):
ai ¼ ni=Ai
maxðn=AÞ ð2Þ
where ai = the estimated preference coefficient for the i-th
host, ni = the number of eggs laid on the i-th host,
Ai = the availability of the i-th host (fresh biomass in g,
dry biomass in g, sum of tiller heights in cm of tiller), and
max(n/A) = the maximum number of eggs laid per unit
of a host, adjusted for relative plant availability, across the
different hosts. Oviposition on each available host plant
can in turn be determined using equation (3):
ni ¼ ntotalaiAi
PI
i¼1
aiAi
ð3Þ
Where ni = the estimated relative oviposition selection in
number of eggs or oviposition events for the i-th host,
ntotal = the total number of eggs or oviposition events laid
across all hosts, ai = the estimated preference coefficient
for the i-th host, and Ai = the availability of the i-th host.
Relative oviposition preference coefficients as affected
by host treatment were estimated with least squares non-
linear regressions (JMP; SAS Institute, 2002) using equa-
tion (3). Coefficients with overlapping 95% confidence
intervals [parameter estimate � SE 9 t(a/2, d.f. error) with
t(a/2, d.f. error) = 1.975] were not considered different. In
addition, the number of eggs per oviposition event was
compared among host treatments using a one-way ANOVA
(Proc MIXED). The ANOVA model included ‘cage’ and
‘cage*host treatment’ as random effects. The total number
of plants receiving eggs for each host treatment (replicates)
varied (n = 2–13). Pearson correlations among preference
coefficients and LS means of selected plant characteristics
were determined using Proc CORR (SAS Institute, 2008).
Larval development duration estimation
Using estimates from van Leerdam (1986), larval devel-
opment duration in degree days (ºD>T0) was estimated
for each larva or pupa recovered from a plant dissec-
tion that produced an adult. Van Leerdam (1986) stud-
ied E. loftini immature development durations at
temperatures between 20 and 32 °C on both artificial
diet and sugarcane stalk sections. Results derived from
van Leerdam (1986) suggest that egg and pupal devel-
opment durations in ºD>T0 are approximately constant
regardless of food source (87.5 ºD>13.6 °C for eggs,
and 124.9 ºD>14.0 °C and 121.6 ºD>13.8 °C for male
and female pupae, respectively). Duration to complete
larval development on artificial diet is 349.3 ºD>14.9 °Cand 378.1 ºD>14.6 °C for males and females, respec-
tively (van Leerdam, 1986).
For each recovered immature, the time of larval eclosion
was estimated by summing ºD from the day subsequent to
moth release at 12:00 hours until the duration of the egg
stage was attained. Time of pupation was estimated by
summing ºD from the day of adult eclosion at 12:00 hours
backwards until the pupal stage was attained. When pupae
were recovered during plant dissection, larval develop-
ment occurred exclusively on the plant, and ºD between
larval eclosion and pupation were computed directly.
When larvae were recovered, development occurred on
the plant and subsequently on diet. Thus, total larval
development duration on the plant was estimated using
equation (4):
Dtotalij ¼P
disecl
�Dij
1�P
pupdis
�Dij
Dtotaldiet
ð4Þ
where Dtotalij = the estimated total larval development
duration on the i-th host for the j-th larva,P
disecl
�Dij = the
sum of ºD from larval eclosion to plant dissection on the
i-th host for the j-th larva,P pup
dis�Dij = the sum of ºD on
artificial diet from plant dissection to pupation for the j-th
larva recovered from the ith host, and Dtotaldiet = the total
larval development duration on artificial diet (van Leer-
dam, 1986). This approach assumed that larval develop-
ment on artificial diet after plant dissection was not
affected by prior feeding on the host plant. Because sub-
stantial interplant movement of neonates occurred within
each cage under our experimental conditions, all host
treatments were infested with E. loftini, and the duration
Oviposition and larval development of Eoreuma loftini 335
of larval development could be estimated for males and
females on all host treatments.
Larval development durations were compared using a
two-way ANOVA with host treatment and sex as factors
(Proc MIXED). Larvae for which relative development on
plant prior to dissection 1�P pupdis
�Dij=Dtotaldiet was less
than 0.15 were eliminated from the analysis because their
development was considered abnormally slow (a relative
larval development of 0.15 corresponds to late first or early
second instars; van Leerdam, 1986). The total number of
plants with at least one recovered immature for each host
treatment (replicates for host treatment) varied (n =6–13). ANOVA random effects included ‘cage’ and ‘cage*host treatment’. When fixed effects were detected
(P<0.05), the Tukey-Kramer adjustment (a = 0.05) was
used to separate LS means. In addition, multiple contrasts
compared selected groups of host treatments (Proc
MIXED) with P-values adjusted using the step-down Bon-
ferroni method (Proc MULTTEST). Pearson correlations
between LS means of development durations and prefer-
ence coefficients, and LSmeans of selected plant character-
istics, were determined using Proc CORR.
Results
Plant physical characteristics and free amino acid concentrations
The host treatments presented a wide range of biomass,
tiller, and leaf availability to moths and larvae (Tables 1
and 2). On 5–6 weeks after oviposition, brome and rye-
grass were still in vegetative development but showed
broken, desiccated injured tillers because of larval feeding.
For young rice, non-injured tillers were between milk and
hard dough stages, whereas injured tillers exhibited dead
panicles in the boot or panicle exertion stages. Intermedi-
ate and older rice exhibited non-injured tillers withmature
panicles and senescent foliage; however, tillers sustaining
E. loftini boring injury during panicle exertion displayed
whiteheads (blank panicles with dead grain). For perennial
grasses, young johnsongrass and vaseygrass exhibited
maturing and mature seed heads, respectively. Intermedi-
ate and older johnsongrass showed young vegetative tillers
growing from rhizomes in addition to flowering and
mature tillers with dispersed seeds. Intermediate and older
vaseygrass displayed a mixture of vegetative, flowering,
mature, and senescing tillers.
Concentrations of FAAs, whether in leaves or stems,
were variable and numerous differences between host
treatments, phenological stages, and leaf vs. stem tissues
were found (Table 3). Threonine, glutamate, and alanine
were detected in leaves and stems of all host treatments,
whereas methionine was only detected in leaves of older
johnsongrass. Cystine was only detected in leaves of
intermediate and older johnsongrass. For more than 70%
of sampled plants, when threonine, glutamate, alanine,
and glycine were detected in leaves, they were also detected
in stems. In rice, glutamate and serine represented 17–42% and 36–37%, respectively, of all FAAs detected in
leaves and stems (Table 3). In rice stems, aspartate was
also abundant, representing 28–38% of detected FAAs.
In vaseygrass, alanine represented 20–89% of all FAAs
detected in leaves and stems. Proline represented more
than 20% of FAAs in brome, intermediate ryegrass, and
intermediate johnsongrass (Table 3). The first and second
principal components accounted for 27.0 and 24.3%,
respectively, of the variance in the FAA concentration
dataset (data not shown). The biplot summarizing the rel-
ative positions of host treatments and FAA concentrations
in leaves and stems over the first two principal compo-
nents did not provide additional information (data not
shown).
Eoreuma loftini oviposition
A total of 5 965 E. loftini eggs were observed during this
study, 99.5% of which were laid in clusters (283 clusters
observed). Thirty-one eggs laid singly were also
observed. Hereafter, the deposition of eggs, whether
singly or in clusters, is referred to as an ‘oviposition
event.’ Of the oviposition events, 96.5% occurred in –and 99.2% of the eggs were laid in – folds of dry plant
material, leaf, or leaf sheath. The mean (� SE) number
of eggs per oviposition event was 19.0 � 1.0 and
showed limited differences (F8,46 = 2.00, P = 0.068)
among host treatments (Figure 1).
Preference coefficients for the number of eggs and ovi-
position events per g plant fresh biomass, per g plant dry
biomass, and per cm of tiller accounted for about 60% of
variability in the observed oviposition data (P<0.05;Figure 2). Rice was more preferred than non-crop grasses
with young, intermediate, or older rice having preference
coefficients equal to 1 regardless of preference estimation
method (Figure 2). Young brome, young johnsongrass,
and young and intermediate ryegrass had preference coef-
ficients equal to zero because oviposition did not occur on
these hosts (Figure 2).
Based on the number of eggs per g of plant fresh bio-
mass, older rice was the most preferred host (Figure 2),
followed by intermediate rice (76% as preferred), and
intermediate and older perennials (24–37% as preferred).
Preference for intermediate brome was lower than that for
older rice (6% as preferred), but was not different from
that for other hosts. The variability of preference for young
rice and vaseygrass was high as shown by large standard
errors (Figure 2). Thus, although preferences were low
for these young hosts, differences with preferences for
336 Beuzelin et al.
Table1
Riceandnon-cropgrassplantcharacteristics(LSmeans)recorded
duringEoreumaloftiniovipositionpreference
andlarvaldevelopmentassessmentin
agreenhouse
experim
ent,
Beaumont,TX,U
SA,2009
Hosttreatm
ent1
Ovipositionassessment
Developmentassessment
Age
2
(weeks)
Fresh
weight3(g)
Dry
weight3(g)
No.
tillers
Sum
of
tiller
heights(cm)
No.
leaves
No.
dry leaves4
Ratioofdry
leavesto
greenleaves
No.
tillers
Sum
oftiller
heights(cm)
Tillerstem
diameter(m
m)
Rice
Young
58.8fg
1.6cd
4.6ef
243.2e
20.8fg
2.2e
0.12ef
5.5de
317.3e
3.7b
Interm
ediate
958.5c
17.4b
8.5bcd
604.9bcd
50.5cd
12.8cd
0.34cd
10.4cd
656.7cd
3.7b
Older
1345.1d
17.0b
6.8de
468.3d
47.4cd
23.7a
1.04a
8.2de
523.9cde
4.0b
Johnsongrass
Young
619.9e
3.1cd
2.0f
148.5ef
12.1g
0.3e
0.03f
2.2e
265.4e
5.1a
Interm
ediate
1066.1c
20.2b
4.3ef
565.3cd
38.1def
10.8cd
0.41c
6.0de
728.9c
4.1b
Older
1478.9b
29.0a
5.2def
648.3bc
47.5cd
22.5a
0.95a
5.8de
704.1c
3.8b
Vaseygrass
Young
719.2e
3.5c
6.8de
271.3e
26.3efg
3.7e
0.18def
8.2de
426.9de
3.0c
Interm
ediate
12102.8a
26.8a
12.2b
1043.9a
69.8b
16.2bc
0.30cde
19.4b
1549.6a
3.6bc
Older
1760.5c
18.2b
11.5bc
903.0a
61.7bc
25.7a
0.74b
15.6bc
1174.8b
3.7b
Brome
Young
60.8g
0.2d
2.5f
59.0f
10.8g
1.2e
0.13ef
9.5cd
297.9e
2.1de
Interm
ediate
1013.1ef
4.1c
7.2de
270.2e
40.6de
10.2d
0.33cd
10.3cd
312.2e
2.3d
Ryegrass
Young
61.3g
0.2d
8.1cde
134.0ef
26.0efg
0.8e
0.04f
33.8a
1212.9b
1.5f
Interm
ediate
109.0fg
1.4cd
24.5a
726.2b
104.8a
20.0ab
0.24cde
27.1a
1038.9b
1.6ef
F12,144(allP<0.001)
251.43
242.64
53.06
95.10
49.17
61.76
60.66
40.60
52.31
71.13
Leastsquaresmeanswithinacolumnwiththesameletterarenotdifferent(TukeyorTukey-Krameradjustment:a=0.05).
1Leastsquaresmeansreported
onaperplantbasis,exceptforyoungannualgrasses(twoplants).
2Plantagepost-emergence.Larvaldevelopmentassessmentwassubsequentto
plantd
issection5–6weeks
afterovipositionassessment.
3Estim
ated
from
five
separaterepresentative
plants.
4�one-thirdleafwasdry.
Oviposition and larval development of Eoreuma loftini 337
Table2
Contrastscomparingplantcharacteristicsrecorded
duringEoreumaloftiniovipositionpreference
andlarvaldevelopmentassessmentin
agreenhouse
experim
ent,Beaumont,
TX,U
SA,2009
Comparison
(d.f.=1.144)
Ovipositionassessment
Developmentassessment
Fresh
weight
Dry
weight
No.
tillers
Sum
of
tiller
heights
No.
leaves
No.dry
leaves
Ratioof
dryleaves
togreen
leaves
No.
tillers
Sum
of
tiller
heights
Tiller
stem
diameter
Non-cropgrassesvs.rice
0.08
8.3*
11.99*
3.31
3.03
4.79
34.55*
36.67*
51.47*
72.54*
Perennialsvs.rice
186.15*
99.56*
0.50
49.15*
1.36
0.17
4.63
2.19
57.62*
0.97
Annualsvs.rice
382.19*
402.59*
42.00*
33.82*
4.55
27.91*
93.62*
120.89*
24.17*
388.78*
Perennialsvs.annuals
1449.89*
1202.08*
47.54*
212.04*
1.55
44.87*
82.64*
129.71*
6.24*
595.71*
Bromevs.rice
252.18*
246.48*
5.92*
88.97*
16.74*
43.08*
48.38*
2.06
13.67*
183.21*
Johnsongrassvs.rice
100.87*
95.81*
18.13*
0.34
5.43
2.81
1.10
8.09*
2.02
26.15*
Ryegrassvs.rice
283.34*
319.51*
176.28*
0.09
58.66*
5.18
85.29*
287.67*
142.20*
378.62*
Vaseygrassvs.rice
184.64*
56.16*
30.03*
133.6*
18.77*
5.69
7.17*
29.22*
137.50*
11.63*
Johnsongrassvs.vaseygrass
12.57*
5.26*
94.84*
120.43*
44.13*
16.50*
2.65
68.05*
106.18*
72.68*
Johnsongrassvs.brome
618.17*
598.03*
1.89
99.11*
4.13
25.64*
36.19*
15.84*
24.69*
327.96*
Johnsongrassvs.ryegrass
666.45*
709.15*
291.92*
0.68
94.59*
0.60
68.81*
380.43*
113.49*
577.55*
Vaseygrassvs.brome
785.90*
501.87*
53.80*
390.88*
63.47*
75.63*
20.80*
11.55*
201.24*
109.93*
Vaseygrassvs.ryegrass
840.21*
604.06*
70.15*
113.16*
14.32*
19.45*
46.79*
147.04*
2.06
269.20*
Bromevs.ryegrass
0.76
3.94*
205.68*
69.51*
115.07*
15.32*
4.33
200.83*
203.38*
29.23*
*P<0.05
usingthestep-downBonferroniadjustmentformultiplecontrasts.
338 Beuzelin et al.
Table3
Freeam
inoacidconcentrations(pmolofFAAperllofjuice)inrice
andnon-cropgrasses(LSmeans)inagreenhouseexperim
ent,Beaumont,TX,U
SA,2009
Hosttreatm
ent
Tissue
EssentialFAAs
Non-essentialFAAs
Arginine
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Valine
Alanine
Aspartate
Cystine
Glutamate
Glycine
Proline
Serine
Tyrosine
(a)IndividualFAAs
Rice Young
Stem
s8
0d0d
0b0c
00d
32e
27bcd
4d589bcd
0b521cd
37c
0ef
317b
0c
Leaves
35103cd
35bcd
90ab
18bc
021bcd
93e
138bcd
10d
170def
0b868ab
128bc
0ef
346b
0c
Interm
ediate
Stem
s10
38d
86abcd
86ab
0c0
0d39e
219b
4d826bc
0b712bc
30c
0ef
254b
0c
Leaves
37118cd
0d23b
0c0
28bcd
55e
74bcd
6d21ef
0b315def
143bc
0ef
234b
0c
Older
Stem
s49
20d
158a
106ab
98abc
00d
161cde
434a
11d
1833a
0b1124a
155bc
0f2386a
0c
Leaves
1673cd
0d0b
0c0
0d70e
66bcd
7d260def
0b480cde
630a
94cde
770b
0c
Johnsongrass
Young
Stem
s0
0d0d
0b0c
00d
2e0d
1d9ef
0b29f
0c0ef
7b0c
Leaves
034d
0d0b
0c0
0d2e
22cd
1d0f
0b9f
13c
0ef
3b0c
Interm
ediate
Stem
s0
0d0d
0b0c
00d
3e0d
1d7ef
0b14f
0c87def
2b0c
Leaves
020d
18cd
0b0c
00d
18e
14cd
1d0f
39b
9f10c
164bcd
7b0c
Older
Stem
s11
18d
23cd
0b39abc
0102ab
42e
111bcd
2d133def
0b47f
38c
0ef
41b
28c
Leaves
1735d
40bcd
0b0c
161
76abcd
22e
117bcd
2d16ef
604a
15f
86c
0ef
34b
0c
Vaseygrass
Young
Stem
s129
26d
0d0b
0c0
0d92e
0d3296bcd
13ef
0b142ef
16c
0ef
59b
369bc
Leaves
146
339a
0d0b
0c0
0d443b
0d11222a
0f0b
105f
82c
0ef
153b
178c
Interm
ediate
Stem
s301
75cd
12cd
0b11bc
026bcd
344b
92bcd
2005bcd
543cde
0b580bcd
123bc
0ef
366b
964a
Leaves
1713
111cd
0d0b
0c0
0d277bcd
0d5208bc
12f
0b76f
119bc
0ef
15b
0c
Older
Stem
s132
286ab
15cd
0b0c
091abc
651a
195bc
1477cd
1098b
0b316def
408ab
0ef
2066a
720ab
Leaves
915
184bc
0d0b
0c0
0d302bc
0d6323ab
23ef
0b94f
223bc
0ef
102b
59c
Brome
Young
Leaves
9218d
151ab
123ab
118abc
0160a
98de
79bcd
19cd
53def
0b361cdef
240bc
485a
62b
32c
Interm
ediate
Stem
s88
21d
68abcd
0b118abc
071abcd
42e
46bcd
5cd
20def
0b115f
28c
250b
23b
0c
Leaves
670d
0d0b
32abc
064abcd
38e
32bcd
4d5ef
0b97f
40c
230bc
19b
0c
Ryegrass
Young
Leaves
121
9d129abc
209a
171a
063abcd
90de
81bcd
17cd
87def
0b514bcd
124bc
245b
50b
16c
Interm
ediate
Stem
s26
5d0d
0b134ab
00cd
10e
29bcd
3d14ef
0b75f
21c
226bc
0b0c
Leaves
018d
0d0b
66abc
010bcd
20e
36bcd
4cd
5ef
0b84f
28c
256b
26b
0c
Hosttreatm
entF
11,48
1.48
16.54
6.77
8.96
6.29
0.86
10.04
37.27
6.24
11.78
17.96
3.00
27.71
7.27
39.67
12.04
7.33
P>F
0.164
<0.001
<0.001
<0.001
<0.001
0.560
<0.001
<0.001
<0.001
<0.001
<0.001
0.003
<0.001
<0.001
<0.001
<0.001
<0.001
Tissue(hosttreatm
ent)
F 11,42
1.05
10.31
4.25
2.37
2.75
1.02
1.78
11.06
10.23
6.09
23.64
3.63
16.33
5.11
3.09
18.31
8.31
P>F
0.420
<0.001
<0.001
0.022
0.009
0.444
0.090
<0.001
<0.001
<0.001
<0.001
0.001
<0.001
<0.001
<0.001
<0.001
<0.001
Oviposition and larval development of Eoreuma loftini 339
Table3Continued
Hosttreatm
ent
Tissue
TotalFAAs
EssentialFAAs
Non-essentialFAAs
(b)Grouped
FAAs
Rice Young
Stem
s1535.8efg
66.8b
1469.0cde
Leaves
2054.7efg
533.2ab
1521.5cde
Interm
ediate
Stem
s2303.0defg
477.7ab
1825.3bcde
Leaves
1055.7fg
335.9ab
719.8de
Older
Stem
s6533.8bcde
1025.9ab
5507.8bcd
Leaves
2465.7cdefg
225.4ab
2240.3bcde
Johnsongrass
Young
Stem
s47.8g
2.0b
45.8e
Leaves
84.5g
58.0b
26.5e
Interm
ediate
Stem
s113.0g
2.7b
110.3e
Leaves
299.6fg
70.0b
229.6e
Older
Stem
s636.5fg
347.6ab
288.9e
Leaves
1224.3fg
467.1ab
757.3de
Vaseygrass
Young
Stem
s4143.1bcdefg
247.1ab
3896.0bcde
Leaves
12669.0a
928.1ab
11740.0a
Interm
ediate
Stem
s5441.9bcdef
861.8ab
4580.1bcde
Leaves
7531.1abc
2100.7a
5430.4bcd
Older
Stem
s7456.3bcd
1370.6ab
6085.7bc
Leaves
8224.3ab
1401.4ab
6822.9ab
Brome
Young
Leaves
2089.7cdefg
839.3ab
1250.4cde
Interm
ediate
Stem
s894.0fg
453.1ab
440.9de
Leaves
628.4fg
234.1ab
394.4de
Ryegrass
Young
Leaves
1925.2efg
872.8ab
1052.4cde
Interm
ediate
Stem
s544.0fg
204.9ab
339.1de
Leaves
553.6fg
150.0ab
403.6de
Hosttreatm
entF
11,48
16.70
3.08
13.46
P>F
<0.001
0.003
<0.001
Tissue(hosttreatm
ent)F11,42
5.76
1.02
4.65
P>F
<0.001
0.449
<0.001
Leastsquaresmeanswithinacolumnwiththesameletterarenotdifferent(Tukey-Krameradjustment:a=0.05).
340 Beuzelin et al.
intermediate and older hosts were not always detected.
Based on the number of eggs per g of plant dry biomass,
young rice was the most preferred host (Figure 2).
Intermediate brome, intermediate and older vaseygrass,
and intermediate and older johnsongrass were 7–32% as
preferred. Based on the number of eggs per cm of tiller,
older rice was the most preferred host (Figure 2). The
pattern for preference based on the number of eggs per
cm of tiller was comparable to that of preference based
on the number of eggs per g of plant fresh biomass.
However, when the sum of tiller heights was used as a
measure of plant availability, differences were greater
between preferences for young and intermediate rice
(0.55 vs. 0.22), and between preferences for young and
older rice (0.79 vs. 0.46).
Based on the number of oviposition events per g of
plant fresh biomass and per cm of tiller, intermediate rice
was the most preferred host (Figure 2). Preferences based
on fresh biomass and cm of tiller were less for the most
preferred stage of johnsongrass (51 and 40%, respectively)
and vaseygrass (53 and 52%, respectively). Based on the
number of oviposition events per g of plant dry biomass,
young rice was the most preferred host (Figure 2). Corre-
lations among preference coefficients predicting numbers
Figure 1 Number of Eoreuma loftini eggs per oviposition event
(LSmeans + SE) on rice and four non-crop hosts. ANOVA
did not detect differences among host treatments (P>0.05).
B
A
Figure 2 Oviposition preference coefficients (+ SE) predicting the number of Eoreuma loftini (A) eggs and (B) oviposition events, based
on – from left to right – fresh weight, dry weight, or sum of tiller heights asmeasures of plant availability. Coefficients estimated using non-
linear least-squares regressions range from 0 (no oviposition) to 1 (maximumpreference, marked with *). Bars capped with the same letter
are not different using overlap of 95% confidence intervals.
Oviposition and larval development of Eoreuma loftini 341
of eggs (r = 0.767–0.951, P<0.05) and among those pre-
dicting numbers of oviposition events (r = 0.732–0.937,P<0.05) were detected. In addition, correlations between
preference coefficients predicting numbers of eggs and
those predicting numbers of oviposition events were
detected (r = 0.666–0.949, P<0.05).Preference coefficients were not correlated with the
number of dry leaves per plant and stem diameter
(P>0.05; Table 4). However, preference coefficients pre-
dicting numbers of eggs and oviposition events based on
fresh biomass and sum of tiller heights were positively cor-
related with the ratio of dry to green leaves (P<0.05;Table 4). Preference coefficients based on dry biomass
were not associated with the ratio of dry to green leaves
(P>0.05; Table 4). Preference coefficients were not corre-
lated with total, essential, and non-essential FAA concen-
trations (P>0.05; Table 5). When considering individual
FAAs, preference coefficients were positively correlated
with concentrations of serine in leaves, and of aspartate,
glutamate, and valine in stems (r = 0.348–0.838, P<0.05).Concentrations of proline in stems were negatively corre-
lated with preference coefficients (r = �0.514 to �0.620,
P<0.05).
Larval development duration
Eoreuma loftini larval development duration changed with
host treatment (F12,90 = 10.45, P<0.001; Figure 3) but dif-
ferences between male and female larvae were not detected
(F1,410 = 1.02, P = 0.31). In addition, the host treat-
ment*sex interaction was not significant (F12,410 = 0.55,
P = 0.88). Development duration on johnsongrass was
not different from that on vaseygrass, and on brome it was
not different from that on ryegrass (Table 6). Larval devel-
opment was 1.4-fold longer on non-crop grasses than on
rice (Figure 3). However, while development was 1.7-fold
longer on the perennials than on rice, differences in devel-
opment durations between annuals and rice were not
detected (P>0.05; Table 6). Development durations were
not affected by plant stage, except for larvae that developed
1.5-fold slower on young rice than on intermediate and
older rice (Figure 3). Correlations between larval develop-
ment durations and oviposition preference coefficients
were not detected (0.29<P<0.61). Larval development
duration was not correlated with plant availability estimates
(P>0.05), excluding a positive association with stem diame-
ter (P<0.05; Table 4). Development durations were not
correlated with total, essential, and non-essential FAA con-
centrations (P>0.05; Table 5). When considering individ-
ual FAAs, larval development durations were negatively
correlated with concentrations of glutamate, isoleucine,
leucine, and lysine in stems (r = �0.632 to �0.750,
P<0.05).
Discussion
Eoreuma loftini oviposition preference is greater for rice
than for four primary non-crop hosts occurring in Gulf
Coast rice agroecosystems, based on plant fresh biomass,
dry biomass, and sum of tiller heights. Reay-Jones et al.
(2007a) found rice more attractive for oviposition than
sugarcane based on plant dry biomass. Among non-crop
hosts, Showler et al. (2011) reported that E. loftini ovipos-
ited a greater proportion of eggs on johnsongrass than on
vaseygrass. In our study, however, E. loftini showed com-
parable oviposition preferences for these two perennial
grasses. Our data also suggest that under choice condi-
tions, E. loftinimoths will lay a limited number of eggs on
brome and ryegrass.
Eoreuma loftini eggs were laid almost exclusively in folds
on dry plant material regardless of plant host, confirming
Table 4 Pearson correlations (n = 13) of oviposition preference coefficients with Eoreuma loftini larval development durations and
selected plant physical characteristics
Larval
development
duration No. dry leaves
Ratio of dry
leaves to green
leaves
Tiller stem
diameter
r P r P r P r P
Preference coefficient
Eggs per g fresh weight �0.320 0.29 0.438 0.14 0.604 0.029 0.461 0.11
Eggs per g dry weight �0.266 0.38 0.220 0.47 0.355 0.23 0.436 0.14
Eggs per cm of tiller �0.269 0.37 0.528 0.064 0.694 0.009 0.452 0.12
Oviposition events per g fresh weight �0.234 0.44 0.381 0.20 0.505 0.079 0.459 0.12
Oviposition events per g dry weight �0.173 0.57 0.128 0.68 0.221 0.47 0.403 0.17
Oviposition events per cm of tiller �0.156 0.61 0.482 0.095 0.601 0.030 0.462 0.11
Larval development duration 1 – 0.015 0.96 0.033 0.91 0.556 0.048
342 Beuzelin et al.
that E. loftini oviposition preference is associated with the
availability of folds in dry leaf material (Showler & Castro,
2010b). This behavior may explain why young plants are
not preferred. In addition, variations in oviposition have
been associated with characteristics of live plant material
(Reay-Jones et al., 2007a; Showler & Castro, 2010a,b).
Reay-Jones et al. (2007a) and Showler & Castro (2010a)
found that differences in foliar FAA concentrations might
have a role in E. loftini preference between genotypes of
the same host plant species, and between plants of the
same genotype under different levels of stress. The lack of
association between E. loftini oviposition preference and
detectable FAA concentrations among host plant species
in our study suggests that FAA concentrations might not
have an influential role in determining preference among
species or phenological stages within species (Showler &
Reagan, 2012). Some herbivores, such as Spodoptera exigua
(H€ubner), prefer hosts with greater amounts of essential
FAAs (Showler, 2001, 2012). Eoreuma loftini oviposition
preference, however, is likely to be affected more by other
morphological and biochemical factors than by amounts
of FAAs (AT Showler, unpubl.). These factors include rela-
tive amounts of certain sugars (AT Showler, unpubl. data).
Additional factors potentially affecting E. loftini oviposi-
Table 5 Pearson correlations (n = 13) of Eoreuma loftini oviposition preference coefficients and larval development durations with plant
FAA concentrations
Total FAAs Essential FAAs Non-essential FAAs
in leaves in stems in leaves in stems in leaves in stems
r P r P r P r P r P r P
Preference coefficient
Eggs per g fresh weight �0.022 0.944 0.430 0.143 �0.091 0.768 0.190 0.534 �0.009 0.978 0.458 0.116
Eggs per g dry weight 0.046 0.882 0.335 0.264 �0.022 0.943 0.020 0.947 0.055 0.859 0.382 0.198
Eggs per cm of tiller �0.066 0.831 0.392 0.185 �0.120 0.696 0.217 0.476 �0.053 0.864 0.409 0.166
Oviposition events
per g fresh weight
0.067 0.827 0.353 0.236 �0.012 0.970 0.080 0.796 0.077 0.802 0.392 0.186
Oviposition events
per g dry weight
0.191 0.532 0.278 0.357 0.073 0.813 �0.087 0.778 0.200 0.512 0.339 0.258
Oviposition events
per cm of tiller
�0.011 0.971 0.295 0.329 �0.045 0.884 0.106 0.730 �0.005 0.987 0.319 0.289
Larval development
duration
0.239 0.431 �0.124 0.687 0.133 0.666 �0.339 0.257 0.244 0.422 �0.074 0.809
Table 6 Contrasts comparing Eoreuma loftini larval development
durations on rice and four non-crop hosts in a greenhouse
experiment, Beaumont, TX, USA, 2009
Comparison (d.f. = 1,90)
Larval
development
duration
Non-crop grasses vs. rice 40.48*
Perennials vs. rice 63.70*
Annuals vs. rice 0.61
Perennials vs. annuals 38.35*
Brome vs. rice 0.31
Johnsongrass vs. rice 68.05*
Ryegrass vs. rice 0.40
Vaseygrass vs. rice 20.58*
Johnsongrass vs. vaseygrass 2.38
Johnsongrass vs. brome 36.22*
Johnsongrass vs. ryegrass 28.52*
Vaseygrass vs. brome 12.28*
Vaseygrass vs. ryegrass 10.04*
Brome vs. ryegrass 0.02
*P<0.05 using the step-down Bonferroni adjustment for multiple
contrasts.
Figure 3 Eoreuma loftini larval development durations
(LSmeans + SE) in degree days (ºD>T0). Bars with the same
letter are not different (Tukey-Kramer adjustment: P<0.05).
Oviposition and larval development of Eoreuma loftini 343
tion preference include leaf pubescence, as shown for Dia-
traea saccharalis (Fabricius) (Sosa, 1990), and green leaf
volatiles, as shown for Chilo partellus Swinhoe (Birkett
et al., 2006; Midega et al., 2011). The study of physical
and chemical characteristics potentially affecting E. loftini
oviposition preference will assist in better understanding
the insect’s biology and help identify host plant resistance
traits.
Our study is the first to show that E. loftini larvae infest-
ing rice, brome, and ryegrass develop faster than those
infesting johnsongrass and vaseygrass. Although van Leer-
dam (1986) found that female larval development was
slower than that of males, such differences were not
detected in our study. Van Leerdam (1986) estimated that
larvae feeding on sugarcane (cv. NCo 310) stalk sections
completed development in 519 ºD>14.6° C for females
and 392 ºD>14.9° C for males in the laboratory. The fast-
est larval development in our study was 540 ºD, whichoccurred when neonates infested rice at the panicle exer-
tion stage. Thus, E. loftini larval development might be
shorter on sugarcane than on rice and the four non-crop
hosts of our study.
Physical constraints associated with stem diameter may
impact E. loftini immature performance because larger
stems are more suitable for development (Showler et al.,
2011). Nevertheless, the large-stemmed perennials in our
study were less suitable as E. loftini hosts than rice and
annuals that had relatively narrow stems. In addition,
E. loftini larvae were observed feeding within stems but
also extensively through stem walls of rice and annuals.
These observations suggest that physical factors allowing
larvae to escape stem diameter constraints may influence
E. loftini immature performance. Martin et al. (1975) and
Keeping & Rutherford (2004) showed that sugarcane
internode rind hardness is a source of larval antibiosis for
the stem borers D. saccharalis and Eldana saccharina
Walker. Stem fiber and relative lignin contents may also
affect larval feeding and development (Rutherford et al.,
1993).
Host plant nutritional quality is another key factor in
determining E. loftini immature performance. Increased
FAA concentrations have been consistently associated with
enhanced nutritional quality of herbivore host plants
(Showler, 2001; Reay-Jones et al., 2007a; Showler & Cas-
tro, 2010a). However, the quantification of FAA concen-
trations in rice and four primary non-crop hosts in our
study did not help explain differences in E. loftini larval
development durations. Nevertheless, studies utilizing
varying nitrogen fertilization levels to change host plant
nutritional quality demonstrated impacts on herbivore
immature performance. Greater total nitrogen content in
cotton,Gossypium hirsutum L., shortened immature devel-
opment duration in S. exigua (Chen et al., 2008). For Ses-
amia calamistis Hampson feeding on maize, Zea mays L.,
greater stem and leaf nitrogen concentrations increased
larval survival and pupal weight (S�etamou et al., 1993).
Increases in plant total nitrogen and FAA concentrations
result in greater survival, weight, and shorter development
duration for E. saccharina larvae on sugarcane (Atkinson
& Nuss, 1989). Although exact mechanisms enhancing
immature performance for S. exigua, S. calamistis, and
E. saccharina are undetermined, changes in plant FAA and
nitrogen content, nitrogen to carbohydrate ratio, and
potential decreases in defensive compounds are likely
involved (Atkinson & Nuss, 1989; S�etamou et al., 1993;
Chen et al., 2008). Similar to these three lepidopteran her-
bivores, exact causes for differences in E. loftini immature
performance as affected by host plant species and phenol-
ogy have not been determined. In addition to FAAs, host
plant-specific carbohydrate composition (AT Showler,
unpubl.), nitrogen to carbohydrate ratio, and allelochemi-
cals certainly impact nutritional quality. For example,
johnsongrass produces dhurrin (Nicollier et al., 1983), a
cyanogenic glucoside associated with decreased herbivory
(Woodhead & Bernays, 1978).
For crambid and pyralid stem borers, the relationship
between oviposition preference and immature perfor-
mance on crop, forage, and weedy plants seems species-
specific. In our study, E. loftinimoths preferred laying eggs
on rice, which was also themost suitable host, allowing rel-
atively shorter larval development. However, brome and
ryegrass, which seemed more suitable as E. loftini hosts
than johnsongrass and vaseygrass, were the least preferred
hosts. Showler et al. (2011) showed that increased E. lof-
tini oviposition preference for corn, compared with sor-
ghum, Sorghum bicolor (L.) Moench, and sugarcane, was
associated with increased performance, as measured by the
number of adult exit holes. In the same study, oviposition
preference and immature performance were greater on
johnsongrass than on vaseygrass. Eldana saccharina shows
oviposition preference for wild graminoid hosts as com-
pared to corn (Atachi et al., 2005; Conlong et al., 2007).
However, performance is inversely associated with prefer-
ence on these hosts, with longer immature development,
lower survival, and lower pupal weight observed on wild
grasses than on corn (Shanower et al., 1993; Atachi et al.,
2005). Chilo partellus consistently prefers Pennisetum
purpureum Schumach., a forage grass, for oviposition
(Ofomata et al., 2000; van den Berg et al., 2001; Midega
et al., 2011). However, immature survival is extremely low
on this grass (Ofomata et al., 2000; van den Berg et al.,
2001).
The time a herbivore is exposed to a new host, the rela-
tive abundance of hosts, the herbivore feeding habits, and
344 Beuzelin et al.
the suppression from natural enemies as affected by the
host apply the selection pressure shaping the relationship
between preference and performance (Thompson, 1988).
Presumably native to northwest Mexico, E. loftini
expanded its range into easternMexico before it was intro-
duced into south Texas, from where it spread along
>600 km of Gulf Coast within 30 years (Reay-Jones et al.,
2007b). During this range expansion, E. loftini has likely
been exposed to substantial changes in relative abundance
of graminaceous crops, non-crop graminoids, and natural
enemies. Eoreuma loftini preference and performance in
our study are the results of changing selection pressures
and could not have been predicted. In addition, preference
and performance may vary within and among populations
(Thomspon & Pellmyr, 1991; Assefa et al., 2009). Thus,
the study of both preference and performance along with
governing morphological and biochemical factors will
continue to be needed to identify sources and sinks of
E. loftini populations in agroecosystems.
Our study provided insights on aspects of E. loftini
oviposition preference and immature performance, which
impact egg partitioning among primary hosts and the
length of larval development on these hosts in Texas Gulf
Coast rice agroecosystems. Host selection can be predicted
based on oviposition preference and host availability using
equation (3) (Wilson & Gutierrez, 1980; Murphy et al.,
1991; Reay-Jones et al., 2007a). Similarly, larval develop-
ment duration can be used to predict E. loftini dynamics
on primary hosts. However, host-specific survival and
fecundity, which are key performance parameters impact-
ing population dynamics, have not been determined. In
addition, potential E. loftini larval movement and prefer-
ence, which may substantially impact larval mortality and
infestations when hosts occur in mixture, have not been
documented. Together with previous research (Reay-Jones
et al., 2007a; Beuzelin et al., 2011a; Showler et al., 2011),
our study contributes to a foundation for a pest manage-
ment strategy based on the prediction of the relative con-
tribution of multiple host plants to E. loftini populations
in rice agroecosystems.
Acknowledgments
This work was supported by USDA CSREES Crops-
At-Risk IPM program grant 2008-51100-04415 and
USDA NIFA AFRI Sustainable Bioenergy program grant
2011-67009-30132. We thank David Blouin, Mike Stout,
Rita Riggio, Bill White, Lee Tarpley, Ronnie Porter,
Veronica Abrigo, Jaime Cavazos, Becky Pearson, Sebe
Brown, Jannie Castillo, and Jiale Lv for their technical
assistance. We thank David Blouin, Mike Stout, and Eric
Webster for participating in the review of the manuscript.
This study is approved for publication by the Director of
the Louisiana Agricultural Experiment Station as manu-
script number 2012-263-7423.
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APPENDIX A: INSECT NURSERY SITE MAP
Sorghum Fertilization Study
Appendix C
Bioenergy Test
Multiple Infestation Levels
Appendix B
Host Plant
Resistance Test
2012
Appendix D
Host Plant
Resistance Test
2011
Appendix D
26 Rows
23 Rows
7 Rows
5 Rows
North
Canal
Sugarcane & Energycane planted on 11/2/11
Sorghum planted on 4/20/2012
2 row/bed Approx 20 in row spacing 1 seed every 3.6 in Approx. 1 in deep
Buffer 15 ft < 113
5 ft
72 ft R4 838 113 845 5140 1002 M81E 5200 R4
5 ft
72 ft R3 113 5200 845 838 M81E 5140 1002 R3
5 ft
72 ft R2 1002 M81E 5140 113 845 5200 838 R2
5 ft
72 ft R1 845 5140 1002 5200 838 M81E 113 R1
5 ft
Buffer 15 ft <
838
Rows --> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
CANAL CANAL CANAL CANAL CANAL CANAL CANAL CANAL CANAL CANAL CANAL CANAL
Variety Test
APPENDIX B: BIOENERGY TEST 2012 AND 2013 PLOT PLAN
Rep 4
Gap 10 ft
Rep 3
Gap 10 ft
Rep 2
Gap 10 ft
Rep 1
row 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Test Field
Main Plots (N)6 rows 75 ft Fertilization RatesSub plots (Var)2 rows 75 ft control (no nitrogen)
40 lbs N/A (low)
80 lbs N/A (medium)
120 lbs N/A (high)
Bu
ffer
1 r
ow
M8
1E
1-r
ow
Bu
ffer
M8
1E
ES5140 ES5200 ES5140ES5140 ES5200 M81E ES5140 M81E
Appendix C: Beaumont Fertilization Trial 2013-SorghumBuffer 12.5 ft M81E
Buffer 12.5 ft M81E
ES5200 M81E
Total
Length
= 355 ft
26 rows (24 test, 2 buffer) 330 ft
75 ft
75 ft
75 ft
75 ft
M81E ES5200
APPENDIX D: BEAUMONT VARIETY TEST 2011 PLOT PLAN
US
02
-9010
US 02-9010
V
HoCP 08-726 Ho 08-706 L 08-090 L 08-088
Ho 08-711 Ho 08-717 HoL 08-723 L 08-075
L 08-092 L 79-1002 Ho 08-709 HoCP 85-845
HoCP 91-552 Ho 02-113 HoCP 00-950 Ho 05-961
L 07-57 HoCP 04-838 Ho 07-613 blank
IV
L 08-092 L 08-090 blank L 08-088
Ho 08-709 Ho 08-717 HoL 08-723 L 08-075
HoCP 85-845 HoCP 08-726 Ho 08-711 Ho 08-706
Ho 05-961 HoCP 91-552 Ho 02-113 HoCP 00-950
HoCP 04-838 L 79-1002 L 07-57 Ho 07-613
III
HoCP 00-950 L 08-088 L 08-075 Ho 08-717
HoL 08-723 L 08-090 Ho 08-706 Ho 08-711
Ho 08-709 HoCP 04-838 HoCP 85-845 blank
HoCP 08-726 HoCP 91-552 L 79-1002 Ho 02-113
Ho 07-613 L 07-57 Ho 05-961 L 08-092
II
L 08-075 L 08-092 L 08-090 L 79-1002
HoL 08-723 Ho 08-709 Ho 08-717 L 08-088
blank Ho 08-706 HoCP 08-726 Ho 08-711
Ho 02-113 HoCP 85-845 HoCP 00-950 HoCP 91-552
Ho 05-961 L 07-57 Ho 07-613 HoCP 04-838
I
L 08-092 L 08-090 blank Ho 05-961
L 07-57 Ho 07-613 Ho 08-709 L 08-075
Ho 08-717 L 08-088 L 79-1002 HoCP 04-838
Ho 08-706 HoL 08-723 HoCP 08-726 HoCP 00-950
Ho 08-711 Ho 02-113 HoCP 85-845 HoCP 91-552
US 02-9010
Plot size = 1 row, 5.25 ft row width, 12 ft long with 4 ft alley
N Buffer rows on north (6 ft), south (6 ft) and east (1 row) ends of test
APPENDIX D: BEAUMONT VARIETY TEST 2012 PLOT PLAN
North
Plot size: 1 Row, 5.25 ft width, 12ft long with 4 ft alleys
Buffer rows north (6 ft), south (6ft), and 1 row on the east and west borders
1
B
O
R
D
E
R
R
O
W
H
O
C
P
0
2
-
9
0
1
0
~30ft HoCP 02-9010 1
B
O
R
D
E
R
R
O
W
H
O
C
P
0
2
-
9
0
1
0
V
Ho 07-9076 TCP 99-4474 TCP 99-4480 Ho 07-9014 Ho 05-961
TCP 87-3388 Ho 07-9027 CP 89-2143
CP 72-1210 L 08-090 Ho 08-717 Ho 07-9017 L 08-088
Ho 07-613 Ho 02-113 L 79-1002 L 08-092 HoCP 85-845
HoCP 04-838 Ho 08-711 Ho 08-709
IV
Ho 02-113 L 08-092 L 79-1002 Ho 08-711
L 08-088 CP 89-2143 Ho 05-961 TCP 87-3388 Ho 07-9017
L 08-090 CP 72-1210 TCP 99-4480 HoCP 85-845 HoCP 04-838
Ho 07-9027 Ho 07-9076 Ho 08-717 Ho 08-709
Ho 07-9014 Ho 07-613 TCP 99-4474
III
HoCP 04-838 L 08-090 Ho 07-613 HoCP 85-845 Ho 07-9017
CP 89-2143 L 79-1002 Ho 05-961 TCP 87-3388 Ho 08-709
CP 72-1210 Ho 08-711 TCP 99-4480 Ho 07-9076 Ho 07-9027
Ho 08-717 Ho 07-9014 Ho 02-113
L 08-088 TCP 99-4474 L 08-092
II
CP 89-2143 CP 72-1210 Ho 08-711 L 08-090
Ho 07-9014 Ho 05-961 Ho 02-113 L 79-1002 TCP 99-4480
Ho 08-717 L 08-088 TCP 99-4474 Ho 08-709 Ho 07-9027
Ho 07-9017 L 08-092 Ho 07-9076
HoCP 04-838 Ho 07-613 TCP 87-3388 HoCP 85-845
I
TCP 99-4480 CP 89-2143 L 79-1002 TCP 87-3388
CP 72-1210 HoCP 04-838 Ho 07-9076 Ho 07-9014
Ho 05-961 Ho 07-613 Ho 08-709 TCP 99-4474 Ho 08-717
L 08-088 Ho 08-711 Ho 02-113 Ho 07-9027 HoCP 85-845
L 08-092 L 08-090 Ho 07-9017
~12ft HoCP 02-9010
AP
PE
ND
IX E
: S
UN
GR
AN
T 2
010 P
LO
T M
AP
A
PP
EN
DIX
E:
SU
NG
RA
NT
2010 P
LO
T M
AP
A
PP
EN
DIX
E:
SU
NG
RA
NT
2008 P
LO
T M
AP