Insecticide evaluations for soybean aphid management the good

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

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

Mean aphids per plant + SEM Soybean aphid populations

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.

Questions about soybean aphid management in Iowa 1. What products provide the greatest yield protection? 2. What products provide the greatest protection over time? 3. How important is coverage? 4. Is the economic threshold static or dynamic? 5. How do current recommendations hold up in the field?

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

Insecticide efficacy

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?

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

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

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

Commercially available products Rate Active Ingredient Target Application ----------- 3. 2 oz + 4 oz λ-cyhalothrin + chlorpyrifos 0 Cruiser 100 g thiamethoxam ST Cruiser 50 g thiamethoxam ST 50 g + 3. 2 oz thiamethoxam + λ-cyhalothrin ST + 250 Warrior 3. 2 oz λ-cyhalothrin 250 Gaucho 62. 5 g imidacloprid ST 62. 5 g+ 2. 4 oz imidacloprid + cyfluthrin ST + 250 Baythroid 2. 4 oz cyfluthrin 250 Cobalt 13 oz γ-cyhalothrin + chlorpyrifos 250 Lorsban 4 E 16 oz chlorpyrifos 250 Nu. Fos 8 oz clorpyrifos 250 Dimethoate 8 oz dimethoate 250 Penncp-M 2 pt parathion 250 Treatment control zero aphid Cruiser + Warrior Gaucho + Baythroid Treatments were applied 28 July

12000 66 a B ab ab ab 10000 64 ab ab ab b 8000 62 60 6000 58 4000 56 A c 2000 A A A 0 d te a tre trol n U con + d r+ o id e oi h r s r i c r h o d u o u hr rio yt hi Cr arri Ga ayt ar Ba Ap ee W W B Fr t al b Co r Lo an sb os F Nu 54 A A A 52 te oa Di m h et nn Pe p ca -m Mean yield bu per acre (+SEM) Mean cumulative aphid days (+SEM) Available foliar products

12000 66 a a D a a 64 10000 62 b b 8000 60 C 6000 58 C 56 4000 c 2000 c A A 0 ed at rt e ol Un ntr co or rirdi h a Wp ee A fr B 54 A 52 A r ) se (2 X i u Cr 0 g 10 r se ui r C g 50 r+ e s ui or Cr arri W 50 ho uc Ga + o d h uc hroi a G ayt B Mean yield bu per acre (+SEM) Mean cumulative aphid days (+SEM) Available seed treatments

Residual time of labeled treatments 1000 Mean aphids per plant 90 900 70 Untreated Control Aphid Free 600 60 Cruiser 100 80 800 Warrior 50 500 Baythroid 40 400 Cobalt 30 300 Lorsban 20 200 Nu. Fos 10 100 Dimethoate Penncap-m 00 7/30 8/7 8/13 8/17

Experimental Treatments Treatment Target application Rate Active Ingredient ----------- 3. 2 oz + 4 oz λ-cyhalothrin + chlorpyrifos 0 Trimax + NIS 1. 35 oz imidacloprid 250 Trimax + COC + UAN 1. 35 oz imidacloprid 250 1. 35 oz + 2. 4 oz imidacloprid + cyfluthrin 250 spirotetramat + COC 4 oz spirotetramat 250 spirotetramat + COC 6 oz spirotetramat 250 Trimax + spirotetramat + COC 1. 35 oz + 4 oz imidacloprid + spirotetramat 250 Trimax + spirotetramat + COC 1. 35 oz + 6 oz imidacloprid + spirotetramat 250 spirotetramat + COC 4 oz spirotetramat 400 spirotetramat + COC 6 oz spirotetramat 400 potassium silicate 0. 5% v/v potassium silicate 250 potassium silicate 1% v/v potassium silicate 250 control zero aphid Trimax + Baythroid + COC

a 14000 a ab ab 12000 C 66 ab ab ab C C b b 10000 61 b 8000 6000 56 c B B c c 4000 51 2000 A A 0 ed at l e tr tro d hi Un con Ap ee Fr x+ a im Tr OC C a im Tr x+ A at A A at at A at m x m m tra ima tram ax ium % am am ra ) tra e r r + t t s. 5 s. 0 e m e e ) o Tr e t te ax id rot ot Tri tas te 0 tas e 1 ro (400 irot 400 Spir z + r ro i i i o ir m thro Spi z p P lica Po icat o Sp oz + T ay Sp oz ( Sp oz S oz o 4 sil 4 6 B 6 6 S NI 46 Mean yield bu per acre (+SEM) Mean cumulative aphid days (+SEM) Experimental treatments

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.

Insecticide Coverage

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

Droplet size Coarse Same volume Fine

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

Experimental Treatments Tee. Jet 11002 Twin Jet Tee. Jet 8001 Extended Range

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

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

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

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

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

Conclusions • Improved coverage = Improved control • Improved control = Improved yield – 1. 6 bu per acre • Coverage is more important that product • What about systemic products?

Economic thresholds

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

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

Points to consider • The current economic threshold is dynamic not a static 250 aphids per plant. D. W. Ragsdale, B. P. Mc. Cornack, R. C. Venette, B. D. Potter, I. V. Mac. Rae, 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 – However ……

12000 66 a B ab ab ab 10000 64 ab ab ab b 8000 62 60 6000 58 4000 56 A c 2000 A A A 0 d te a tre trol n U con + d r+ o id e oi h r s r i c r h o d u o u hr rio yt hi Cr arri Ga ayt ar Ba Ap ee W W B Fr t al b Co r Lo an sb os F Nu 54 A A A 52 te oa Di m h et nn Pe p ca -m Mean yield bu per acre (+SEM) Mean cumulative aphid days (+SEM) Labeled foliar treatments

In the Field

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

Treatments Treatment Insecticide Time of Application Control Preventative IPM approach Seed treatment Warrior + Headline Warrior Cruiser R 1 -R 2 250 aphids per plant seed treatment

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

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

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

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.

Acknowledgements • USDA • Funding from Iowa Soybean Association • Industry Partners – – – – – Bayer Crop. Science BASF Cheminova Dow Agro. Sciences FMC Nu. Farm PQ Syngenta Valent • Graduate students – Nick Schmidt – Wayne Ohnesorg

Questions?

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