This study evaluated the persistence of the fungal biocontrol agent Metarhizium anisopliae conidia applied beneath cover crop canopies for sugarbeet root maggot management over three years from 2002-2004. The results showed that conidial counts decreased significantly 30-60 days after application, with higher degradation rates for spray applications compared to granular formulations. Microclimate conditions like soil temperature and moisture varied under different cover crop treatments and likely influenced conidial persistence. Overall, cover crops provided a unique microenvironment that allowed conidia to persist longer than in open fields, and lower seeding rates of cover crops combined with microbial applications had advantages.

1. 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

3. Research component 2 (cereal cover crops) Cover crops + terbufos reduced root injury (Dregseth et al. 2003) Oat 186 seeds/m 2 Rye 186 seeds/m 2 Oat 374 seeds/m 2 Rye 374 seeds/m 2 seeds/m 2 Non-cover sugarbeet plot

4. Research component 3 ( M. anisopliae F52) Pure culture of F52 Granular formulation (on corn meal carrier) Infected SBRM 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 10 12 viable conidia/ha, as soil incorporated granule or spray at the base of plants

5. Years: 2002-2004 Location: Pembina Co. Split-plot design Main plot: seeding rates (0, 186, 374 seeds/m 2 ) 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

7. PROC ANOVA: 2002 & 2003 conidial persistence 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 <0.0001 Cover 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 0.0254 Error (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 - - Combined analysis not possible. Formulation and sampling date had significant effect on conidial persistence. Conidial counts were averaged formulation X sampling date

8. 2002 results: F52 Formulation X Sampling date 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

9. 2003 results: F52 Formulation X Sampling date 80 ± 136 a 6 ± 27 a Observation: Detecting conidia in soil is difficult (dilution effect) Finding: Spray form lost 90% conidia in 30 days (2 yr) 3189 ± 2413 b 310 ± 411 a

10. PROC ANOVA: 2004 conidial persistence Source df Mean square F P Replication 3 16791.945 1.39 0.2682 Cover type 1 83.364 0.01 0.9152 Error (a) (Replication x Cover type) 3 6226.715 - - Seeding rate 2 4552.400 0.35 0.7169 Cover type x Seeding rate 1 7070.494 0.54 0.4826 Error (b) (Replication x Cover type x Seeding rate) 9 13180.971 - - Formulation 1 1387151.420 145.50 <0.0001 Cover type x Formulation 1 573.018 0.06 0.8097 Seeding rate x Formulation 2 3449.191 0.36 0.7023 Cover type x Seeding rate x Formulation 1 3990.279 0.42 0.5274 Error (c) (Replication x Cover type x Seeding rate x Formulation) 15 11073.077 - - Sampling date 1 1093204.911 70.67 0.0035 Error (d) (Replication x Sampling date) 3 15468.986 - - Cover type x Sampling date 1 1545.637 0.13 0.7235 Seeding rate x Sampling date 2 3509.930 0.29 0.7503 Formulation x Sampling date 1 1222780.369 101.18 <0.0001 Error (e) 26 12085.752 - - Formulation and sampling date had significant effect on conidial persistence. Conidial counts were averaged formulation X sampling date and…

11. 2004 results: F52 Formulation X Sampling date Observation: High variability in conidial detection between years Finding: Spray form lost >90% conidia in 30 days (3 yr)

12. Cover crop microenvironment 30 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.) Microclimate under cover crops (May-July): What was going on in the cover crop microenvironment? WatchDog 425 & Watermark sensor 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

14. 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?