ESA ANNUAL MEETING 2009

Persistence of Metarhizium anisopliae conidia applied beneath a cover crop

canopy for sugarbeet root maggot management

Ayanava Majumdar, Ext. Specialist, Auburn University, AL

Mark A. Boetel, Assoc. Prof., North Dakota State University

Stefan T. Jaronski, USDA-ARS NPARL, Sidney, MT

10x

Research component 1 (SBRM)

Tetanops myopaeformis (Diptera: Ulidiidae):10 to100%

yield loss (Cooke 1993)

Research component 2 (cereal cover crops)

Oat 186 seeds/m2

Rye 186 seeds/m2

Oat 374 seeds/m2

Rye 374 seeds/m2 seeds/m2

Non-cover sugarbeet plot

Cover crops + terbufos reduced root injury

(Dregseth et al. 2003)

Research component 3 (M. anisopliae F52)

Pure culture of F52 Granular formulation(on corn meal carrier)

InfectedSBRM larva

USDA-ARS scientists demonstrated efficacy of F52 against SBRM larvae (Jonason et al. 2005, Campbell et al. 2006)

In this study: F52 rate 8 x 1012 viable conidia/ha, as soil incorporated granule or spray at the base of plants

Years: 2002-2004

Location: Pembina Co.

Split-plot design

Main plot: seeding rates (0, 186, 374 seeds/m2)

Sub plot: biocontrol formulations

FIELD SAMPLING

4 samples per plot

Sampling time: 0 and 30 or 60 days after tret.

Stainless steel core sampler

Sampler disinfected between each sample

Samples transported under cool conditions

Persistence study methodology

LABORATORY PROCESSING

Serial dilution with 1 g soil sample (Goetel & Inglis 1997)

100 micro L plated on modified Chase medium, replications = 4

Colony forming units (CFUs) counted at 10 days

2 g subsample for soil moisture estimation >> CFUs adjusted

Plates were scanned

• Mean CFU counts were subjected to Analysis of Variance

• Folded F-test: to determine feasibility of combined analysis

• Treatment means from significant interaction terms were analyzed by using LSD at P = 0.05

Data analyses

2002 2003

Source df Mean square F P Mean square

F P

Replication 3 1051.809 0.95 0.4286 219.123 1.38 0.2693

Cover type 4 884.037 0.74 0.5850 159.059 1.24 0.3474

Error (a) (Replication x Cover type)

12 1201.300 - - 128.788 - -

Formulation 1 58639.035 45.41 <0.0001 5824.284 45.93 <0.0001Cover type x Formulation

4 1045.222 0.81 0.5383 149.918 1.18 0.3583

Error (b) (Replication x Cover type x Formulation)

15 1291.292 - - 126.811 - -

Sampling date 1 42610.296 31.87 0.0110 4360.104 17.25 0.0254Error (c) (Replication x Sampling date)

3 1337.127 - - 252.688 - -

Cover type x Sampling date

4 1118.789 1.01 0.4174 132.279 0.83 0.5150

Formulation x Sampling date

1 58379.415 52.94 <0.0001 3931.208 24.81 <0.0001

Cover type x Formulation x Sampling date

4 773.560 0.70 0.5977 129.339 0.82 0.5260

Error (d) 27 1102.7245 - - 158.462 - -

PROC ANOVA: 2002 & 2003 conidial persistence

Combined analysis not possible.

Formulation and sampling date had significant effect on conidial persistence.

Conidial counts were averaged formulation X sampling date

2002 results: F52 Formulation X Sampling date2002

1397 ± 1283a610 ± 544a

1409 ± 897a

11428 ± 6521b

0

2000

4000

6000

8000

10000

12000

0 30 60

CF

Us

per

g d

ry s

oil

610 ± 544 a

11428 ± 652 b

1409 ± 897 a 1397 ± 1283 a

Observation: Choosing formulation/delivery system is critical to conidial persistence

Finding: Granular formulation may be benefited by soil microenvironment

0

5000

10000

15000

1 2 3

M. anisopliae granules M. anisopliae spray

11428 ± 6521b

610 ± 544a

1409 ± 897a

1397 ± 1283a

2003 results: F52 Formulation X Sampling date

2003

6 ± 27a80 ± 136a

310 ± 411a

3189 ± 2413b

0

500

1000

1500

2000

2500

3000

3500

0 30

CF

Us

per

g d

ry s

oil

80 ± 136 a 6 ± 27 a

Observation: Detecting conidia in soil is difficult (dilution effect)

0

5000

10000

15000

1 2 3

M. anisopliae granules M. anisopliae spray

11428 ± 6521b

610 ± 544a

1409 ± 897a

1397 ± 1283a

Finding: Spray form lost 90% conidia in 30 days (2 yr)

3189 ± 2413 b

310 ± 411 a

Source df Mean square F PReplication 3 16791.945 1.39 0.2682Cover type 1 83.364 0.01 0.9152Error (a) (Replication x Cover type) 3 6226.715 - -Seeding rate 2 4552.400 0.35 0.7169Cover type x Seeding rate 1 7070.494 0.54 0.4826Error (b) (Replication x Cover type x Seeding rate)

9 13180.971 - -

Formulation 1 1387151.420 145.50 <0.0001Cover type x Formulation 1 573.018 0.06 0.8097Seeding rate x Formulation 2 3449.191 0.36 0.7023Cover type x Seeding rate x Formulation 1 3990.279 0.42 0.5274Error (c) (Replication x Cover type x Seeding rate x Formulation)

15 11073.077 - -

Sampling date 1 1093204.911 70.67 0.0035Error (d) (Replication x Sampling date) 3 15468.986 - -Cover type x Sampling date 1 1545.637 0.13 0.7235Seeding rate x Sampling date 2 3509.930 0.29 0.7503Formulation x Sampling date 1 1222780.369 101.18 <0.0001Error (e) 26 12085.752 - -

PROC ANOVA: 2004 conidial persistence

Formulation and sampling date had significant effect on conidial persistence.

Conidial counts were averaged formulation X sampling date and…

2004

118 ± 343a137 ± 262a 2441 ± 1717a

53185 ± 20366b

0

10000

20000

30000

40000

50000

60000

0 30

Days after treatment

CF

Us

per

g d

ry s

oil

2004 results: F52 Formulation X Sampling date

0

5000

10000

15000

1 2 3

M. anisopliae granules M. anisopliae spray

11428 ± 6521b

610 ± 544a

1409 ± 897a

1397 ± 1283a

Observation: High variability in conidial detection between years

Finding: Spray form lost >90% conidia in 30 days (3 yr)

Cover crop microenvironment30 day conidial degradation rates:

Oat + Granule = 81% (2 year av.)

Rye + Granule = 78% (2 year av.)

Oat + Spray = 88% (3 year av.)

Rye + Spray = 92% (3 year av.)

What was going on in the cover crop microenvironment?

WatchDog 425 & Watermark sensor Microclimate under cover crops (May-July):

Degradation rates Soil Temp. (C)

Water tension (kPa)

Low rate OAT G: 63%, S: 84% 18 23

High rate OAT

G: 100%, S: 92% 21 36

Low rate RYE G: 80%, S: 95% 19 20

High rate RYE G: 75%, S: 88% 19 25

No cover 17

Sampling time & technique are important for assessing persistence

Detection of conidia in disturbed soils could be difficult

Cover crops provide unique microenvironment under the canopyLower rate of cover crop + microbial has advantages

(stable microenvironment, ease of application)

Microbial formulation/delivery technique is important for increasing persistenceConidia persisted 30-60 days

Overall recommendations

ACKNOWLEDGEMENT

Research specialists: Robert Dregseth, Allen Schroeder

Cooperators: Baldwin Farm (Pembina Co., ND)

Statistics & data interpretation: Dr. Richard Horsley

Funding agency: USDA Pest Management Alternatives Program

QUESTIONS?