Insecticide evaluations for soybean aphid management: the good, the bad and their residual times

1. Insecticide evaluations for soybean aphid management: the good, the bad and their residual times Kevin D. Johnson and Matt O’Neal Soybean Entomology Lab Department of Entomology

2. Soybean aphid impact • Damage • Phloem “sap” feeding • Sooty mold • Virus vectoring • ~25% yield reduction documented in Iowa • Possible economic loss of $163 per acre* * Assuming 65 bu per acre and $10 per bu

3. Soybean aphid populations Mean aphids per plant + SEM

4. Insecticide use in Iowa soybeans • 2003 ~ 4 million acres • 2004 ~100-250,000 acres • 2005 ~2 million acres • 2006 ~100-250,000 acres • 2007 ~4-5 million acres Photo Purdue Univ.

5. Questions about soybean aphid management in Iowa • What products provide the greatest yield protection? • What products provide the greatest protection over time? • How important is coverage? • Is the economic threshold static or dynamic? • How do current recommendations hold up in the field?

6. Cumulative aphid days • A good way to visualize treatment differences • Analogous to degree days • Estimate plant exposure to aphids • Examples • 10 aphids for 10 days = 100 CAD • 100 aphids for 10 days = 1000 CAD • 1,000 aphids for 10 days = 10,000 CAD

7. Insecticide efficacy

8. Questions involving insecticides for soybean aphid management • What insecticides protect soybean yield from aphids? • What insecticides last for the longest period of time following application?

9. Materials and Methods • 32 Treatments in a Randomized Complete Block Design • 6 replications in 2007 • 1 Location

10. Statistical analysis • Aphid population data required log transformation • Yield data did not require transformation • Analyzed using an one-way analysis of variance (ANOVA) • Treatment differences were determined significant at P < 0.05

11. Aphid arrival and peak populations Control Treatment Aphid Peak Location Arrival Population Date Floyd 11 June 915 13 Aug Plots were planted on 15 May

12. Commercially available products Treatments were applied 28 July

13. Available foliar products Mean cumulative aphid days (+SEM) 12000 66 a Mean yield bu per acre (+SEM) B ab ab ab ab ab 64 10000 ab ab ab 62 b 8000 60 6000 58 4000 56 A c 2000 54 A A A A A A A A A 0 52 Cruiser + Warrior Gaucho + Baythroid Dimethoate Baythroid Penncap-m Untreated control Lorsban NuFos Aphid Free Cobalt Warrior

14. a a A A Aphid free Warrior Available seed treatments Mean cumulative aphid days (+SEM) 12000 66 Mean yield bu per acre (+SEM) D a a 64 10000 62 b b 8000 60 C 6000 58 C 56 4000 c c 54 B 2000 A 52 A 0 50 Cruiser 50g Cruiser + Warrior Gaucho Untreated control Cruiser 100g (2X) Gaucho + Baythroid

15. 1000 900 800 700 600 500 400 300 200 100 0 7/30 7/30 8/7 8/7 8/13 8/13 8/17 8/17 100 90 80 70 60 50 40 30 20 10 0 Residual time of labeled treatments Untreated Control Mean aphids per plant Aphid Free Cruiser 100 Warrior Baythroid Cobalt Lorsban NuFos Dimethoate Penncap-m

16. Experimental Treatments

17. Experimental treatments Mean cumulative aphid days (+SEM) a 14000 a 66 Mean yield bu per acre (+SEM) ab ab ab ab ab C 12000 C C b 61 b b 10000 8000 56 c B B 6000 c c 4000 51 2000 A A A A A A A A 0 46 Spirotetramat 4 oz + Trimax Spirotetramat 4 oz Potassium silicate 0.5% Spirotetramat 4 oz (400) Spirotetramat 6 oz (400) Spirotetramat 6 oz + Trimax Potassium silicate 1.0% Spirotetramat 6 oz Trimax + COC Trimax + Baythroid Trimax + NIS Untreated control Aphid Free

18. Conclusions • Timing is more important that product selection • Multiple insecticide applications did not protect yield beyond a single insecticide application. • Insecticides applied at 250 aphids per plant provide consistent yield protection. • Seed treatments did not prevent economic injury level. • Seed treatments lack residual activity to control aphids.

19. Insecticide Coverage

20. Insecticide coverage objective • Determine if application technique influences aphid control when using: • Pyrethroids • Organophosphates • Tank-mixes (Pyrethroids and Organophosphates)

21. Droplet size Fine Coarse Same volume

22. Droplet size and coverage 250 Microns 250 Microns = 500 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns

23. Experimental Treatments TeeJet 11002 Twin Jet TeeJet 8001 Extended Range

24. Materials and Methods • 9 Treatments in a Randomized Complete Block Design • 6 replications • 3 Years • 2 Locations

25. Peak aphid populations Control Treatment Peak County and Year Population Date Floyd 2007 563 18 August Story 2007 1121 14 August Floyd 2006 171 11 August Floyd 2005 413 31 August

26. Experimental treatments Mean yield (+SEM) A 65 64 AB A AB A 63 62 AB AB B 61 60 59 C 58 57 56 55 Very fine Untreated Aphid Free (Very fine) Fine Medium Medium Very fine Medium Very fine Controls Pyrethroids Organophos. Tank-mix

27. Effect of chemistry Mean yield (+SEM) 65 64 63 62 61 60 59 58 57 56 55 Pyrethroids Organophosphate Tank-mix

28. Effect of coverage 65 Mean yield (+SEM) 64 63 A 62 61 B 60 59 58 57 56 55 Medium Very fine

29. Conclusions • Improved coverage = Improved control • Improved control = Improved yield • 1.6 bu per acre • Coverage is more important that product • What about systemic products?

30. Economic thresholds

31. Dynamic Thresholds Economic injury level is the point where the cost of control = the damage caused by the pest Economic injury levels are not static! • EIL = * 100 • C = Cost of control (pesticide + application) • V = Market value • Y = Yield

32. EIL = * 100 EIL ET Dynamic Thresholds Aphid per plant Time

33. Points to consider • The current economic threshold is dynamic not a static 250 aphids per plant. • However …… • D. W. Ragsdale, B. P. McCornack, R. C. Venette, B. D. Potter, I. V. MacRae,E. W. Hodgson, M. E. O’Neal, K. D. Johnson, R. J. O’Neil, C. D. Difonzo, T. E. Hunt, P. Glogoza, and E. M. Cullen 2007. • Economic Threshold for Soybean Aphid. • Journal of Economic Entomology 100(4) 1258-1267

34. Labeled foliar treatments Mean cumulative aphid days (+SEM) 12000 66 a Mean yield bu per acre (+SEM) B ab ab ab ab ab 64 10000 ab ab ab 62 b 8000 60 6000 58 4000 56 A c 2000 54 A A A A A A A A A 0 52 Cruiser + Warrior Gaucho + Baythroid Dimethoate Baythroid Penncap-m Untreated control Lorsban NuFos Aphid Free Cobalt Warrior

35. In the Field

36. Testing recommendations in the field. • 4 Treatments in a Randomized Complete Block Design • 6 replications • 3 Years • 2 Locations each year

37. Treatments Treatment Insecticide Time of Application Control Preventative Warrior + Headline R1-R2 IPM approach Warrior 250 aphids per plant Seed treatment Cruiser seed treatment

38. Peak aphid populations Control Treatment Peak Year County Population Date 2007 Story 2765 18 August Lucas 356 6 August 2006 Story 6 8 August Lucas 21 9 August 2005 Story 290 6 September Lucas 60 8 September

39. Story County 2007 A 60000 Mean cumulative aphid days (+SEM) 50000 40000 B B 30000 B B 20000 B 10000 0 Untreated Preventative Preventative + IPM IPM + 250 Seed trt + 250 250

40. Story County 2007 70 Mean yield bu per acre (+SEM) A A A A A 60 50 B 40 30 Untreated Preventative Preventative + 250 IPM IPM + 250 Seed trt + 250

41. Conclusions • Scout the field!!!!! • Multiple insecticide applications did not protect yield. • Preventative treatments did not maintain aphid populations below the threshold. • Preventative treatments did not protect yield.

42. Acknowledgements • USDA • Funding from Iowa Soybean Association • Industry Partners • Bayer CropScience • BASF • Cheminova • Dow AgroSciences • FMC • NuFarm • PQ • Syngenta • Valent • Graduate students • Nick Schmidt • Wayne Ohnesorg

43. Questions?

44. EIL = * 100 EIL ET Dynamic Thresholds Aphid per plant Time