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Pointers For Insect Pathologists
 

Pointers For Insect Pathologists

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    Pointers For Insect Pathologists Pointers For Insect Pathologists Presentation Transcript

    • Pointers for Insect Pathologists: Lessons from a Bio-based IPM Study Ayanava Majumdar Extension Entomologist Gulf Coast Research & Extension Center, Fairhope, AL Mark A. Boetel Assoc. Prof., Entomology Department North Dakota State University, Fargo, ND Stefan T. Jaronski Res. Entomologist, USDA-ARS Northern Plains Agric. Res. Lab., Sidney, MT
    • Sugarbeet Research Project Integration of cover crops with Metarhizium anisopliae (Ascomycete) for sustainable management of sugarbeet root maggot (SBRM), Tetanops myopaeformis (Diptera: Ulidiidae) Damaged root-tip Heavy scarring Deformed root Av. Yield loss = 40% Major insect in 49% sugarbeet acreage in many states. Significant scarring of root surfaces by SBRM feeding SBRM: healthy & infected
    • Problem of experimental setup Strain of M. anisopliae : ATCC62176 (MA1200) Rate of MA: 8 x 10 12 viable conidia per ha (2x) MA applications: modified-in-furrow granules, postemergence spray Choice of location, design & statistics…do it right the first time! Biomaterials are expensive! X X Red river valley of ND & MN High insect pressure Moderate insect pressure
    • What organism/strain to test?
      • Choice of fungus and strain is problem, few commercial formulations
      • MA persists in disturbed ecosystems:
        • Hallsworth & Magan (1999): 41 to 104 o F
        • Vanninen (1995): <50 o F
        • Bing & Lewis 1993, Bidochka et al. 1998: persistence in disturbed soil
      • Cover crops + conventional i-cides work (Boetel et al. 2000, 2001)
      • MA1200 is pathogenic to SBRM (Jonason et al. 2005) – LT 50 of 10 d at 2.6 x 10 6 conidia/ml
      • Field testing with three concentrations (Campbell et al. 2006) – linear yield response, 2x rate had good results
      • Grower observation: cover crops protect beets from SBRM??
      • Logical next step…Integration of cover crop + MA
    • Cover cropping technique Oats @ 187 & 374 seeds/m 2 Rye @ 374 & 187 seeds/m 2 1 2 3
    • Do you see an effect of pathogen? Results of purely bio-based insect control test can be less encouraging. High insect pressure: MA spray provided similar level of root protection to terbufos (chemical standard) Consistency of trends: weather, high SBRM insect pressure Untreated check plot MA granules only MA spray only Root injury = (0-9 scale) 8-9 5-6 5-6
    • Do you see an effect of integration?
      • Problems with integrated test plots (e.g., cover crop + MA):
      • Yields should not be the only parameter (direct assessment is imp.)
      • Under high insect pressure, effect of one factor (cover crop) could mask treatment differences
      • Under low to moderate insect pressure, root injury data were consistent with rate of cover crop
      Untreated check plot Root injury = (0-9 scale) 8-9 Oat 374 seeds/m 2 + MA spray 3-4 Rye 374 seeds/m 2 + MA spray 3-4
      • Delivery method:
        • 2.5 x 10 5 conidia/granule coated on corn grit - required large amount of product
        • MIF placement: seed separated from fungus
        • 20% Tween solution was binder
      MA granules: product application & activity Bander MA granules in Noble metering unit 16/20 mesh
      • MA granules should be spread around the seed and applied early
      • Detection of spores in soil is problematic >>>
      • Soil sample at 60 d after treatment indicated delayed sporulation
      • Allow time for the fungus to outgrow and sporulate!
      MA granules: product delivery & activity NA = not available CFUs/g dry soil Treatment 0 DAT 30 DAT 60 DAT 2002 Oat186 + MaG 247 1902 Oat233 + MaG 530 905 Rye374 + MaG 467 1090 Rye466 + MaG 622 1215 MaG 1185 1875 2003 Oat186 + MaG 62 0 NA Oat233 + MaG 125 0 Rye374 + MaG 92 0 Rye466 + MaG 60 30 MaG 62 0 2004 Oat186 + MaG 122 92 NA Oat374 + MaG 122 0 Rye186 + MaG 155 62 Rye374 + MaG 312 0 MaG 92 437
      • Conidia activated before or at spray
      • Targets were the flies & early instars of SBRM
      • Conidia remain in application zone, so placement is critical
      • Expect rapid conidial decline
      MA spray: product delivery & activity NA = not available CFUs/g dry soil Treatment 0 DAT 30 DAT 60 DAT 2002 Oat186 + MaS 8285 1527 NA Oat233 + MaS 10867 1467 Rye374 + MaS 11247 872 Rye466 + MaS 16430 1527 MaS 10310 1652 2003 Oat186 + MaS 1580 372 NA Oat233 + MaS 4092 247 Rye374 + MaS 3182 155 Rye466 + MaS 4530 560 MaS 2560 217 2004 Oat186 + MaS 58800 4465 NA Oat374 + MaS 46300 2277 Rye186 + MaS 55800 1655 Rye374 + MaS 55750 2030 MaS 49175 1777
    • Measuring conidia titers in soil (persistence study)
      • Techniques commonly used:
      • Dilution plating: provides reliable results
      • Galleria baiting: provides relative estimates (not recommended for persistence studies)
      MA colonies on Chase medium
      • Soil sampling/plating procedure:
      • Sample using proper equipment (soil core with small diam.)
      • Sample within application zone
      • Mark the pit with flag or stick (avoid resample)
      • Scan plates on flatbed scanner
      • What do we need to know?
      • Soil structure & condition: conidial infectivity low in sandy soil, conidia persist in high water activities (A w )
      • Water removed by vegetation (e.g., cover crops, intercrops, etc.)
      • Temperature in bare vs. shaded soil in treated zone (persistence)
      • Wind movement inside/outside plant canopy (moderates temperature)
      Microsite environment is important How to do it? Soil analysis & cropping history Soil probes: WatchDogs with moisture & temperature probes
    • Summary
      • Focus on ecological approach to microbial research for soil insects
      • Living insecticides should not be assessed as if conventional chemicals
      • Product delivery system should be fine-tuned to target insect
      • Increasing persistence should be the aim…integrated approach can help!
      • Expect wide variances in spore recovery
      • Frequent sampling will provide better picture
    • QUESTIONS?