citrus research and education foundation field day

Citrus Research and Education Foundation

Field Day

Lake Placid Grove, March 7, 2012

CREF Field Day, March 7, 2012 Page 1

Introduction – Arnold Schumann and Jackie Burns, CREC

The 180-acre citrus grove at Lake Placid is being subleased by the Citrus Research and

Education Foundation (CREF) from the Florida Fish and Wildlife Conservation Commission.

http://myfwc.com/viewing/recreation/wmas/lead/lake-wales-ridge/visitor-information/

The grove is located at an altitude of 60-75 feet above mean sea level, and has two soil series;

Satellite sand and Archbold sand. The original trees of ‘Hamlin’ and ‘Valencia’ oranges were

established in about 1990, most on Swingle rootstock. From 1999 to 2001 the grove was

http://myfwc.com/viewing/recreation/wmas/lead/lake-wales-ridge/visitor-information/


abandoned, and the subsequent successful rehabilitation process by the CREC, with help from

Lykes Bros. and others, brought it back to a profitable production level by about 2004, just as the

first canker infections were discovered in the NE block. The first HLB infected trees were

identified in 2007, although the disease was probably already established in the NE corner of the

grove in 2006.

From 2007 until 2009 the grove was surveyed quarterly and HLB-symptomatic trees were

removed and destroyed. Psyllids were controlled with frequent insecticide sprays, but the

intensity of sprays was further increased to about the current 9 per year when it became apparent

that the spread of HLB in the grove was unchecked (Fig. 1). By September 2009, the cumulative

infection was about 8% and further removal of infected trees was stopped because at the

exponential rate of infection observed, we anticipated rapid loss of fruit harvests and economic

collapse of the grove was imminent. From spring 2010 until present the grove has been managed

with a more intensive soil- and foliar- applied fertilizer program (see Table 2 in the additional

Figure 1. Cumulative HLB infection in the entire CREF grove at Lake Placid


information section), more aggressive psyllid control program, and only unproductive trees are

being removed – most of them due to blight infection. The current average HLB infection level

in the grove is estimated to be >80% (Figs. 1 & 2).

Figure 2. Block layout and area (acres, lower number) in the CREF grove (left), and spatial distribution of

HLB infections (right). Blue dots represent the HLB infected trees identified in 2011.


The grove blocks 30, 32 and 27b are planted with mature ‘Hamlin’ orange, the new block 31 is

1-year old ‘Vernia’ on three different rootstocks, and the rest of the grove is planted with mature

‘Valencia’ orange. The yield history for the two main varieties in the grove is shown in Fig. 3,

with an apparent upward trend from 2009/10 to 2011/12. The average ‘Hamlin’ yield for this

harvest season was 514 boxes/acre.

The CREF grove is in a very cold location during winter cold front episodes, being on the

windward side of Lake Istokpoga during a typical freeze night with a north-westerly wind.

During the winter of 2010/11, the air temperature was less than 28 degrees Farenheit for more

than 9 hours during two nights, and for shorter periods on other nights. Fruit losses due to

Figure 3. Average fruit yield of ‘Hamlin’ and ‘Valencia’ in the CREF grove.


freezing, and defoliation of trees was considerable, as shown in photos in the “additional

information” section. Fortunately the affected trees were able to recover and produce the good

crop of fruit we now see in 2012.

The research topics in the program are part of a comprehensive USDA/SCRI block grant entitled

“Management strategies for Huanglongbing-infected groves: decision-making assistance for

the Florida citrus grower”. G.P. Solutions (Labelle, FL) contributed major in-kind support in

the form of their foliar nutrition products which were used in 2010 and 2011 seasons for the

entire grove. The grant funding started in 2009/10 and research results to date are all part of

ongoing work in progress.

Leafminer Research Update – Lukasz Stelinski, CREC

CLM Control with Mating Disruption (Fig. 4):

• Mating disruption of CLM was highly effective for periods of 8 weeks or longer

• Proven effectiveness has been limited to mature groves thus far at the commercially

available rate

• Leaf infestation is reduced prior to mating; therefore, it is a proactive control tool

• Reductions in infestation in grapefruit have been correlated with significantly reduced

levels of canker infection

• Highly pest specific; has no impact on natural enemies or on other pests such as psyllids

• Can be applied by hand or by machine; currently machine application requires

specialized equipment

• Machine application can be contracted in coordination with the company selling the

product

Insecticide resistance monitoring and management (Fig. 5):

• The development of insecticide resistance may become a major obstacle to the successful

management of the Asian citrus psyllid (ACP) if steps to prevent it are not taken now

• The baseline susceptibility data for both adult and immature ACP to commonly used

insecticides were collected for five ACP populations from various parts of Florida from

2009-2011.

• Increased activity of insecticide detoxifying enzymes has been correlated with insecticide

resistance in ACP.

• Five CYP4 genes have been identified that are implicated in development of resistance in

ACP.

• ACP populations in Florida exhibit some level of decreased susceptibility to all registered

insecticides used for their management.

• From 2010 to 2011, resistance levels to two important classes of insecticides (pyrethroids

and organophosphate) increased dramatically for certain Florida populations of ACP.

• Resistance levels have not increased for the neonicotinoids from 2010 to 2011 (Good

news!)


Figure 4. Poster presentation on CLM control


Figure 5. Poster presentation on insecticide resistance


Highlands County Citrus Health Management Areas for Coordinated Area

Sprays – Tim Hurner, Highlands County Extension

Highlands County has Seven Citrus Health Management Areas (CHMAs)

The Highlands CHMAs and their Area Captains are:

Avon Park/Lake Letta CHMA

Lake Letta/Sebring CHMA

Bairs Den CHMA

Area Captain: Steve Farr – Ben Hill Griffin (863) 635-2251

[email protected]

Central Highlands 17/27 CHMA

Area Captain: John Gose – Lykes Brothers (863) 465-4127 [email protected]

East 70 Flatwoods CHMA

Lorida CHMA

Area Captain: Doug Schobert – Premier Citrus (772) 562-5030

[email protected]

Kissimmee River Basin CHMA

Area Captain: Tommy Todd - Lykes Citrus (863) 467-1384 ext.302

[email protected]

Highlands CHMA Psyllid Survey 1/6 – 2/3/2012

CHMA Area Acres* Blocks* Psyllid Count

Avon Park/Lake Letta 2,297 114 98

Lake Letta/Sebring 1407 68 19

Central Highlands US 27 1953 88 164

Bairs Den 4144 187 155

East 70 Flatwoods 398 20 66

Kissimmee Basin 4189 71 67

Lorida 2397 59 10

*Surveyed area

Upcoming CHMA Coordinated Area Spray

The next Coordinated Area Spray will occur in the last half of March or the first week in April

depending on the end of bloom, new flush, and psyllid populations. The chemical will be an O.P.

To be sure you are coordinating with your neighbors; contact your Area Captain to get a

notification of the exact timing of the spray for your CHMA Area.

Go to the CHMA Tool Kit on the CHMA Web Site http://www.flchma.org for a list of

recommended Organophosphates

mailto:[email protected]




http://www.flchma.org/


Figure 6. Citrus Health Management Areas in Highlands County


History of Corymbia torelliana as a Windbreak and Cultural Guidelines - Bill

Castle, Professor Emeritus, CREC

Name: Corymbia torelliana, commonly referred to in Florida as just “torelliana” is related to

Eucalyptus, in fact is was originally known as E. torelliana. Recent studies resulted

in it being placed in its own genus: Corymbia.

Origin: The plant is native to Australia where it is used for land conservation and other

purposes.

Florida History: As a windbreak in Florida, the plant began its life with Chuck Obern, a

vegetable grower west of Clewiston. He planted the species around his property and

internally for wind protection. His trees were mature during the 2004 and 2005

hurricane seasons. One hurricane passed nearby and the torelliana plants sustained

little damage. The performance of this plant at the Obern farm attracted enough

attention to warrant trialing it as a windbreak for canker management in citrus groves.

Characteristics: Fast-growing (they can easily reach 10-12 feet in height in the first full year of

growth under good conditions); relatively large leaves; retain lower branches;

spreading canopy. Are they salt and cold tolerant? Yes, however, their cold

tolerance is still being evaluated. Most evidence so far suggests that they are

considerably more tolerant after one year of good growth. Young trees in colder

locations may not survive. Are they tolerant of calcareous sites? Yes.

Windbreak design: The purpose of a windbreak is to slow the wind, not to establish a wall and

completely block the wind. Therefore, it is not recommended to plant trees closer

than 8 ft. in the row nor more than 12 ft. between trees. Spacing between trees and

the specific design of the windbreak are important economic considerations. The

spacing between trees relates directly to cost as does the number of rows. The latter

is dictated by cost and available space. The torelliana windbreak can be established

as a single row. Some double offset rows have also been planted with rows about 8

ft. apart; however, there is the view that land planted to a windbreak is land not

planted to citrus trees, so devoting up to 15% of flatwoods land to a windbreak is not

acceptable!

Site preparation/tree planting:

Prior to planting, clean the row(s), treat them with a residual herbicide and

incorporate organic matter. This is critical. Nothing assures a good first year

better than site preparation and conducive cultural practices.

Install irrigation. This is critical to insure the best growth possible in Year 1.

Plant in the spring to provide a full growing year. This is critical.

Use nursery plants about 2 ft. tall.

Cultural management:

Irrigate the windbreak plants as if they were citrus trees.

Fertilize the trees regularly with a balanced material the first year or two with

slow-release, dry or liquid.

Weed management may or may not be needed. The basic strategy is to support

the fullest expression of the plant’s vigor and, thus, any weed pressure would be

minimized.


Torelliana plants appear to be quite accepting of, responsive to, mechanical

hedging and topping.

Expectations:

Torelliana plants appear to be broadly suitable for Florida grove site conditions,

but they are responsive to good cultural practices.

The plants are propagated as seedlings. That means the plants display some

variability, i.e., there will be some odd or different plants in the windbreak. Good

WB management probably involves replacing those plants to maintain the

integrity and function of the WB.

Variability is also introduced because of different site conditions related to soil

and drainage. Excellent site preparation, especially adding organic matter, helps

minimize negative site effects.

A double-row WB costs more, but it is a good form of insurance against “holes”

in the WB.

NOTE – Dr. Don Rockwood, Professor Emeritus, School of Forest Resources and

Conservation, has established seed orchards of Torelliana and selected potentially

superior plants. Nursery plants are available.

Information resources:

CREC windbreak website. http://www.crec.ifas.ufl.edu/extension/windbreaks/.

EDIS. http://edis.ifas.ufl.edu/.

o Potential Woody Species and Species Attributes for Windbreaks in Florida.

http://edis.ifas.ufl.edu/fr286.

o Field Guide to Identify the Common Casuarina (Australian Pine) Species in

Florida. http://edis.ifas.ufl.edu/hs394.

o The Benefits of Windbreaks for Florida Growers.


o Management of Field Windbreaks. http://edis.ifas.ufl.edu/fr290.

o Fundamentals of Citrus Canker Management. http://edis.ifas.ufl.edu/pp153.

o Windbreak Designs and Planting for Florida Agricultural Fields.


Advanced Citrus Production Systems (ACPS) – Arnold Schumann, CREC

The third objective of the USDA/SCRI block grant proposal was to “evaluate an advanced

production method for replanting in HLB-endemic groves”. The selected site in the northeastern

side of the grove was ideal for the ACPS because both canker and HLB were first found there

(Fig. 7). The previous ‘Hamlin’ block on the site was destroyed by severe freezes during the

period when the grove was abandoned. The 5.6-acre experiment block was designed primarily

for evaluating and demonstrating different citrus rootstocks and a rooted cutting propagation

method, delivery of fertigation by microsprinkler or drip, and use of controlled release fertilizer

(CRF) (Figs. 7-8). The windbreak trees planted around the block are to help protect the young

citrus trees from rapid infection by canker from the adjacent grove (Fig. 7).

http://www.crec.ifas.ufl.edu/extension/windbreaks/

http://edis.ifas.ufl.edu/

http://edis.ifas.ufl.edu/fr286

http://edis.ifas.ufl.edu/hs394



http://edis.ifas.ufl.edu/pp153



Figure 7. Layout and design of the ACPS experiment. Green dots are trees with drip fertigation, pink dots

are trees with microsprinkler fertigation and blue dots are trees with microsprinkler irrigation and CRF.

Yellow dots are the Torrelliana windbreak trees.

Figure 8. Location of ‘Vernia’ orange on three rootstocks and location of ‘Valencia’

orange rooted cuttings in full rows of the experiment.


The ‘Vernia’ trees were planted out in March 2011 and the ‘Valencia’ rooted cuttings in October

2011. The trees are therefore too young to display meaningful differences at this time and will be

reported on periodically in future to update readers and visitors.

The ACPS block represents a useful prototype design for growers wanting to try out the

technology at a reasonable cost and small scale. Please refer to Figure 9 to identify the main

components which will be discussed during the field day.

Figure 9. Requirements for a small ACPS installation showing labeled

components outside (top) and inside (bottom) the utility shed.


HLB – Tim Spann, CREC

A foliar nutrient spray and fertigation experiment was initiated in early 2010 (Fig. 10) to

compare additional intensive fertilization methods with the conventional dry granular fertilizer

program and standard supplementary micronutrient sprays in HLB-endemic situations. The

objective of this study was to determine the profitability of aggressive HLB-infected tree removal

versus enhanced grove care to sustain production.

In 2010 the cumulative HLB incidence was >20%, and by the end of 2011 it was >80% (Fig. 1).

Large plots of 84 trees each in the 38-acre block were chosen in order to obtain better averaging

of measured parameters across the highly variable HLB infection severity typically seen in

infected groves.

*The high foliar nutrition program included major, secondary and micronutrients applied with

every pesticide spray (see table 2 in additional information section). The plant nutrient elements

used were N, P, K, Ca, Mg, S, Mn, Zn, Mo, B, Fe. Non-nutrient active ingredients were

phosphite as potassium phosphite, salicylic acid as potassium salicylate, and Bacillus subtilis

biofungicide.

Figure 10. Plot layout and experimental procedures for the foliar nutrition / fertigation experiment*.


The standard foliar nutrition program consisted of 1-2 annual applications (April and June,

coinciding with leaf flushes) of Mn, Fe, and Zn at labeled rates of 2 gal/acre (Growers Fertilizer

Corporation liquid 1.6% Fe, 2.0% Fe, 2.0% Zn). The scouting, removal treatment was not

continued after 2010 due to the very high HLB infection rates which would have required

destruction of nearly 25% of the block. We also acknowledged the difficulty of conducting

representative inoculum removal treatment comparisons within the block, without the ability to

block psyllid movement across treatments. Granular fertilizer was applied at a nitrogen rate of

200 lb/acre, split equally four times per year. Calcium nitrate was used as the nitrogen source

when available, or else ammonium nitrate was used. In 2010 calcium nitrate was used in

February and April, while in 2011 it was used in every application. The composition of the

granular fertilizer in 2011 was 10-02-13 + 11.3% Ca, 1.7% Mg, 3.5% S, 0.03% Fe, 0.03% B.

Supplementary fertigation was applied during the early spring and summer to the replications in

the eastern half of the block (Fig. 10). Comprehensive hydroponics nutrient solution (see Figure

12 in the additional information section) at 0.5 lb N /acre equivalent was injected in the daily

irrigation, using an automated Netafim controller. About 20 lb/acre additional nitrogen was

added to the annual total in the fertigated half of the block.

Other horticultural practices were uniform for the experiment block, including daily automated

irrigation, herbicide application, mowing, hedging/topping, and the intensive psyllid control

sprays applied in conjunction with the local CHMA (see table 2 in the additional information

section). Due to the inability to irrigate the entire block at the same time, no irrigation water was

applied for freeze protection. During the winters of 2009/10 and 2010/11 quite severe freeze

damage to fruit and foliage occurred in the block, resulting in a partial yield loss for the 2010/11

season. This 2011/12 winter season was milder and the yield will be estimated and statistically

analyzed.

Four to six-month old spring-flush leaves were collected and analyzed in July each year to assess

the nutritional status of the trees in general and to determine the treatment responses (Table 1).

Most nutrient elements were in the recognized sufficiency ranges except for low concentrations

of manganese (Mn) in treatment 2. The iron concentrations were also in the slightly low range

for the whole citrus block, which matches with some of the leaf nutrient deficiency symptoms

visible in the grove. Significant treatment differences were only detected for leaf P and Fe

concentrations, where values were slightly elevated in the treatment receiving the intensive

nutrient and phosphite sprays.

The results of two HLB disease surveys conducted in the experiment during September 2010 and

March 2011 were analyzed statistically. Cumulative infection levels in the experiment block

were about 35%, but no statistically significant difference could be detected between the

treatments (35.6% and 34.7% for the intensive foliar nutrient spray and standard control

treatments, respectively).


Table 1. Nutrient concentrations of ‘Valencia’ orange leaves in July 2010

Treatment

N P K Mg Ca S B Zn Mn Fe Cu

(% DW) (mg/kg DW)

(2) Control 2.72 0.129 1.11 0.531 3.23 0.334 74.4 30.3 18.8 41.6 34.3

(1) Nutrients+SAR 2.78 0.138 1.21 0.514 3.17 0.322 74.8 33.2 20.2 44.8 33.8

LSD(0.05) 0.102

NS

0.008*

0.125

NS

0.025

NS

0.256

NS

0.033

NS

5.51

NS

4.79

NS

4.21

NS

2.68*

4.32

NS

Citrus nutrition field experiments are generally slow to respond to treatments. At this early stage

of two years since treatments were imposed, there are no apparent differences in tree

performance between the standard and intensive foliar spray + fertigation programs, although the

2011/12 fruit yield has yet to be picked and analyzed.

The experiment might show treatment differences

given enough years, but non-significant results to date

suggest that a comprehensive granular fertilization

program may sustain trees in HLB-endemic groves

without the need for elaborate foliar spray programs.

There is thus scope to rationalize foliar sprays, but

they are a good insurance for situations where the

nutrient supply from root uptake is compromised.

Instead of heavy applications of multiple nutrients at

the same time in sometimes incompatible

combinations, it may be more effective biologically

and economically to apply foliar nutrients separately

at strategic times during the year (pre-bloom, post-

bloom, leaf flushes) to supplement the ground

fertilization program. There are many environmental

and management factors which interact with the HLB

disease complex in a grove. The automated daily

irrigation used in the CREF grove may also be

beneficial by reducing stress on HLB-infected trees,

helping them to survive and continue producing fruit.

Figure 11. Walk-through path for field tour


Additional Information

Spray and fertilizer programs (Where trade names appear, no discrimination is intended, and no

endorsement by the University of Florida is implied)

Tab

le 2

. pes

tici

de

and

inte

nsi

ve f

olia

r n

utr

itio

n p

rogr

am f

or t

he

blo

ck 2

9 ex

per

imen

t 2011

Month

Timing

Product

Rate

/100gal

Foliar nutrients

Pests

Comments

Jan

About mid

month for

urea

Dimethoate 4E

LI 700

1 pint/A

0.25% v/v

Low

biu

ret u

rea:

3.2

6% c

once

ntra

tion

(use

27

lb u

rea

in 1

00 g

allo

ns w

ater

)

ACP

LI 700 added to

buffer pH to 5.5-

6.5

mid Feb

Just prior

to bloom

Danitol

16 oz/A

So

lub

or

(use

1 lb

in 1

00 g

allo

ns w

ater

) C

alci

um

nit

rate

– s

pra

y gr

ade

(use

5 lb

in

100

gallo

ns w

ater

) –

or 9

0 oz

CN

9

ACP

Use 2 lb CN in

aerial spray of 15

gpa (or 36 oz CN9)

Mar/Apr

Avoid pesticides

during bloom

N

itro-

30 S

RN

1 g

al/A

+ R

ecov

erR

X 3

-18-

18

2gal

/A +

Mic

rote

ch A

G 2

qts/

A +

TK

O 0

-29-

26 1

qt/A

+ C

ompa

nion

2-3

-2 1

qt/

A

Apr

Immediately

after bloom

Lorsban

5 pint/A

Mic

rote

ch A

G 2

qts/

A +

8oz

/A S

AR

Act

ivat

or

SA

+ C

ompa

nion

2-3

-2 1

qt/A

ACP

May

Early May

Mustang

4.3 oz/A

Mic

rote

ch A

G 2

qts/

A +

8oz

/A

SA

R

Act

ivat

or +

Com

pani

on 2

-3-2

1 q

t/A

ACP

Jun(1st

summer

oil)

End May to

1st week

June

435 oil

Movento

Delegate

3% v/v

10 oz/A

4 oz/A

Nitr

o-30

SR

N 1

gal

/A +

Rec

over

RX

3-1

8-18

2g

al/A

+ M

icro

tech

AG

2qt

s/A

+ T

KO

0-2

9-26

1qt

/A +

Com

pani

on 2

-3-2

1 q

t/A

Foliar

fungal

diseases

ACP, CRM,

scales

CLM,ACP

Jul(2nd

summer

oil)

End of July

435 oil

Imidan

LI 700

2% v/v

1 lb/A

0.25% v/v

Nitr

o-30

SR

N 1

gal

/A +

Rec

over

RX

3-1

8-18

2g

al/A

+ M

icro

tech

AG

2qt

s/A

+ T

KO

0-2

9-26

1qt

/A +

Com

pani

on 2

-3-2

1 q

t/A

Foliar

fungal

diseases

ACP

LI 700 added to

buffer pH to 5.5-

6.5

Aug

No spray unless

ACP populations

high

Sep

Early Sep

Actara 25WG

435 oil

4 oz/A

2% v/v

Mic

rote

ch A

G 2

qts/

A +

8oz

/A

SA

R

Act

ivat

or

SA

+ C

ompa

nion

2-3

-2 1

qt/A

+

Cal

ciu

m n

itra

te –

spr

ay

grad

e (u

se 5

lb in

10

0 ga

llons

wat

er) –

or 9

0 oz

CN

9

ACP

Foliar

fungal,

CRM

Oct

Mid Oct

Danitol

16 oz/A

Cal

ciu

m n

itra

te –

spr

ay

grad

e (u

se 5

lb in

10

0 ga

llons

wat

er) –

or 9

0 oz

CN

9

ACP

Use 2 lb CN in

aerial spray of 15

gpa (or 36 oz CN9)

Nov

No spray unless

ACP populations

increasing


*Where trade names appear, no discrimination is intended, and no endorsement by the

University of Florida is implied.

Figure 12. Comprehensive hydroponics fertilizer used for supplementary fertigation of mature trees and full

fertigation of young trees*


Management of HLB disease in Maury Boyd’s Orange Hammock grove, 2006 – 2012

Tim Spann, CREC

Efforts to manage HLB affected trees with an intensive nutritional program has become the norm

for many growers. Such a program is only sustainable if the trees continue to produce a quality

crop of fruit. However, when many Florida growers began to seriously look at a nutritional

program as an option there was little data available to quantify the effects of HLB on yield

decline and there was no data about how infected trees performed on a nutritional program.

Beginning in the 2008/09 harvest season we began to collect these data.

Our objective was to track HLB symptomatic and healthy – that is trees in the same grove with

no detectable HLB visually or by PCR – trees of both Hamlin and Valencia varieties over time to

see how they performed on a nutritional management program. At the time the project began

most growers were still removing infected trees so the project was begun in the Orange

Hammock grove in Felda, FL belonging to Maury Boyd. We selected 10 trees of each status

(healthy and HLB symptomatic) for each variety. For Hamlin, the trees were selected from

within two adjacent beds; for Valencia the trees were selected within a single bed. Each year at

harvest the trees are completely stripped and the fruit from each tree are analyzed using the

sizing line in the packinghouse at the CREC. Each individual fruit is weighed and the average

diameter is recorded; a total number of fruit per tree is also calculated.

During the first year, we did a detailed sorting, by hand, of the fruit on the symptomatic trees.

From this we determined that > 95% of all symptomatic fruit (small, lopsided) on symptomatic

trees were less than 2.4 inches in diameter. Thus, by observing the percentage of fruit on a tree

each year that are less than this size we can see if the tree is producing more or less symptomatic

fruit over time.

The tables show some of the data that we have collected to date. Not surprisingly, the HLB

affected trees consistently yield less than the healthy trees and these differences are statistically

significant. However, depending on the year, HLB trees have yielded between about 1.5 boxes

per tree to over 3 boxes per tree – after at least 5 years of known disease infection. Also not

surprising, the HLB affected trees have a greater percentage of fruit < 2.4 inches in diameter, but

this too fluctuates seasonally. Note that the there are fruit on healthy trees < than 2.4 inches;

these are not HLB-symptomatic, but are naturally small fruit.

Statistically, when these data are analyzed, there is no significant interaction between tree health

and year for either yield or percentage of small fruit. This means that the changes that occur from

year-to-year are independent of those changes caused by HLB. Put another way, healthy and

HLB trees respond similarly to environmental changes between seasons. Statistically, the

percentage of small fruit has not changed for either variety over the 4 years of the study. This

means that although the percentage of small fruit does fluctuate from year-to-year, we cannot say

that it is increasing or decreasing at this time. In other words, the HLB affected trees being

observed in this study, on Maury Boyd’s nutritional program, are being maintained and are not

declining.


These data provide support for the belief that HLB affected trees can in fact be maintained and

continue to produce an economically viable crop to sustain our industry until a longterm solution

to HLB is discovered.

Hamlin: Average yield per tree and the average percentage of fruit per tree less

than 2.4 inches in diameter for four harvest seasons.

Avg yield per tree (lbs) % of fruit < 2.4” diameter

Year Healthy HLB Healthy HLB

2008/09 478.4 300.8 1.0 12.6

2009/10 338.3 134.5 6.5 15.7

2010/11 356.4 193.9 5.4 19.8

2011/12 537.5 230.1 1.5 5.9

Valencia: Average yield per tree and the average percentage of fruit per tree

less than 2.4 inches in diameter for three harvest seasons.

Avg yield per tree (lbs) % of fruit < 2.4” diameter

Year Healthy HLB Healthy HLB

2008/09 309.6 145.4 1.0 7.8

2009/10 157.8 144.7 2.5 5.7

2010/11 274.5 180.6 0.4 3.9


Wildlife seen in the CREF citrus grove (Photos by Nolan Rayburn)

Because the CREF grove is surrounded on most sides by the Florida Fish and Wildlife

Conservation Commission’s property, there is an abundance of wildlife in the grove. The deer

are a nuisance because of their browsing of young reset trees but the most troublesome animals

so far have been the feral pigs. On recommendation by the FFWCC, an electrified fence was

constructed around the grove to exclude the hogs, but is understandably having no useful effect.

As the photos show (Fig. 7), the hogs are intelligent animals and will find a way through or

under the fence.

Figure 13. Photographic record of wildlife seen in the CREF grove (photos by Nolan Rayburn)


Damage to the grove from freezing in 2010/11

Figure 8. Fruit and canopy damage from freezes during winter of 2010/11 in the CREF grove.

Figure 14. Freeze damage seen in the grove during February 2011.


Figure 15. Recent photos (December 2011) taken in the CREF grove before the’Hamlin’ harvest.


Acknowledgements*

The CREC and the CREF would like to acknowledge all the people and organizations who

support(ed) the CREF grove and the research at Lake Placid:

Research and support staff of the CREC, especially Kevin Hostler, Troy Gainey, Nolan

Rayburn, Lioubov Polonik, Cynthia Basnaw, Laura Waldo, Ian Jackson, Angelique

Hoyte, and the Grove Management Department

Lykes Bros. – in-kind support during grove rehabilitation

G.P. Solutions – donation of foliar fertilizer products for 2010-2011 ("TKO" Phosphite

0-29-26, Companion Biological Fungicide, Nitro-30 SRN, Microtech AG, Recover-RX

3-18-18, and SAR Activator SA)

USDA/SCRI block grant – funds for experiments conducted from 2010-2012

FDACS BMP research grant – funds for BMP research conducted from 2005-2007

Scotts (now Everris) – donation of Citriblen CRF for BMP research experiment

*Where trade names appear, no discrimination is intended, and no endorsement by the

University of Florida is implied.

citrus research and education foundation field day

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