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Corn Insect Management

Corn Insect Management. Scott Stewart WTREC, Jackson, TN University of Tennessee Extension. The Primary I ssues. Seed treatments, at-planting insecticides A complex of soil insect pests Managing non- Bt corn Primarily for corn borers Bt corn technologies

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Corn Insect Management

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  1. Corn Insect Management Scott Stewart WTREC, Jackson, TN University of Tennessee Extension

  2. The Primary Issues Seed treatments, at-planting insecticides • A complex of soil insect pests Managing non-Btcorn • Primarily for corn borers Btcorn technologies • There are just so many options

  3. Corn Seed Treatments (company offerings)

  4. Relative Efficacy of Corn IST P = poor F = fair G = good E = excellent NL = not labeled

  5. Corn At-planting Insecticides, Trial 12013, Tennessee

  6. Corn At-planting Insecticides, Trial 22013, Tennessee

  7. Capture LFR In-furrow TrialStarkville, MS 2012 (Catchot) All with Poncho 250 Bushels/Acre a ab bc c

  8. Managing Soil Insects • Be proactive in high risk fields • New fields • Problem fields • Cruiser or Poncho 250 not always enough • 500 rates or higher • In-furrow bifenthrin (Capture LFR, Brigade, etc.) • Will also provide protection from cutworms • In-furrow granular insecticides* * Be careful of insecticide/herbicide interactions

  9. Corn Borers • The primary target of Bt corn • Southwestern corn borer • European corn borer • The second generations are typically the most destructive • Because it is larger and affects more acres SWCB ECB

  10. Impact of Infestation Timing on YieldSWCB infested, non-Btplants (Steckel and Stewart) P < 0.0001 A A P < 0.0001 a B a b Weight (g) per Ear b C 2010 2011 Infestation Timing

  11. Treating non-Bt corn in the presence of high corn borer populations (Henry Co., TN)

  12. Scouting Non-Bt Corn • Whorl stage • Pretty easy • Look for windowpane-like lesions on emerging leaves • Remove whorls and unfurl leaves to look for small larvae that are present • Tasseling and later • Much more difficult and requires training

  13. SWCB Moth Trapping • Triggers scouting or spray

  14. SWCB Pheromone TrappingMoths/Trap/Week (Henry Co, TN, 2012) Spray Scout / Spray ActionThresholds No

  15. New Southwestern Corn Borer Threshold(Non-Bt Corn) • Treat prior to tasseling when 5 percent or more of plants are found with egg masses or live larvae • or 7-10 days after pheromone traps catch an average of 50 or more moths on a 7 day catch • Beginning at tasseling (VT) and through the milk stage (R3), treat when 10 percent or more of plants are found with egg masses or live larvae • or 7-10 days after pheromone traps catch an average of 100 or more moths on a 7 day catch

  16. Insecticide SelectionRefer to Local Extension Recommendations First Generation (whorl) • Many labeled pyrethroid insecticides • Baythroid XL • Brigade (bifenthrin) • Karate or Warrior II • Mustang Max • Etc. • Others as in tassel stage Second Generation (tassel) • Intrepid • Belt SC • Besiege • Prevathon • Tracer • Pyrethroids as in whorl stage Direct spray into whorls as much as possible Typically requires aerial application

  17. The Many BtCorn Technologies • Bt corn is the primary means used to control corn borers • Many available Bt trait packages (old and new) • May or may not include Bt traits for western or northern corn rootworm

  18. Relative Efficacy of Selected Bt Corn Traits (see handout for more inclusive list & refuge requirements)

  19. Non-Bt Corn Refuge Requirements • Cotton Counties • 50% for the old technologies • 20% for the new • VT2P, VT3P, SmartStax, Viptera, Optimum Intrasect, Optimum AcreMax • Corn Counties • 20% for the old technologies • 20, 10 or 5 % for the new • Refuge in bag (RIB) system for some Cotton Counties MISSOURI:DunklinNew MadridPemiscotScottStoddard Products with Bt rootworm traits require an “in-field” refuge

  20. Do these refuge requirements make sense?For non-cotton growing areas !!! 5% Refuge of Non-BtCorn • 2+ caterpillar traits, 0 rootworm traits • VT2P, VT2P RIB, Optimum Intrasect, Optimum AcreMax (RIB), and others • 2+ caterpillar traits, 2+ rootworm traits • SmartStax or SmartStax RIB, Optimum Acre XTreme (RIB), and others

  21. Confirmed Resistance to Bt Traits Far and Minor Pest • Fall armyworm to Cry 1F • Herculex or Herculex Xtra • Component of SmartStax, Optimum Intrasect and Optimum AcreMax products • Western corn rootworm to Cry3 Bb1 • VT3 and VT3P • Component of SmartStax • Rotate fields to non-corn crops, rotate Bt rootworm traits, use at-planting insecticide and don’t use Bt rootworm traits if they are not needed Close and Major Pest

  22. SWCB and ECB InjuryCM Tunneling per 20 Stalks (TN, 2010) a P < 0.0001 (LSD = 89.2) b All the Bt lep traits provide near perfect control of SWCB and ECB c c c c

  23. Bt corn in the presence of corn borersYield (Milan, TN, 2011) Bushels/Acre a b

  24. Leaf Injury Score for FAW Catchot, 2010, Starkville, MS Leaf Injury Score (9-1 scale, 9 = no damage) a a b a c c Herculex Optimum Intrasect Viptera

  25. Corn Earworm The most common ear feeding caterpillar

  26. SmartStax Test - 2009 SmartStax (90%) NonBt VT3

  27. SmartStax Test - 2010 NonBt VT3P or SS (40%)

  28. Approximate Reduction in Kernel Damage Compared with Non-Bt Corn(Summarized Across Multiple University Trials, Corn Earworm)

  29. Reality Check Viptera ... “outperforms triple stacks by 14.3 bu/A under significant corn earworm pressure and up to 32 bu/A under heavy pressure”

  30. Yield of Top Ten Hybrids (Bu/Acre)2012 Tennessee Research & Education Center Tests (Allen, et al.)

  31. Insecticide Trial on Non-Bt CornCorn Earworm Injury and Yield (TN, 2011) Application at early silking (moderate pressure) P(yield) = 0.9148 P(kernels) = 0.0013

  32. Insecticide Yield Effects on Non-Bt Corn(Tennessee, Stewart, 2012) A lot of CEW but no treatment effects on kernel injury (P = 0.7341)

  33. Simulated Corn Earworm Injury, Milk StageSteckel and Stewart, 2011

  34. Spraying Corn for Corn Earworm Foliar applications for ear stage infestations of corn earworm in field corn arenot economically practical • No consistent yield response except in presence of southwestern corn borer • Expect little or no benefit on Bt corn (especially the newer traits) • Exposure to insecticides without much yield reward • May create secondary pest problems (spider mites)

  35. Take Home About New Bt Corns University data indicates that the new Bt corn traits will not improve yields in most cases compared with the original Bt technologies • Benefit of reduced refuge requirement • Some potential for improved grain quality and reduced mycotoxins … but not close to a silver bullet • IRM ??? • Corn borers – expect multiple Bt toxins to delay resistance • Corn earworm – exposure to multiple Bt toxins without much reward is concerning

  36. Questions War Eagle!

  37. Aflatoxin Levels in Corn Roy Parker, Texas A&M University, 2011 Test 1 Test 2 No statistically significant differences

  38. Japanese Beetles New Threshold: Treat when 3 or more beetles are present per ear during the first week of silking. Infestations are usually worse along field margins.

  39. Sugarcane Beetles

  40. Final Kernel Damage(cm2/ear in center two rows of plot) Early planting Late Planting P < 0.0045, LSD(0.05) = 0.094, CV = 61.9 P = 0.0428, LSD(0.05) = 0.054, CV = 80.4 a a cm2 damage cm2 damage a ab b b b b

  41. Grain yield (B/A) Early planting Late Planting P = 0.6439, LSD(0.05) = 16.7, CV = 6.4 P = 0.6860, LSD(0.05) = 8.5, CV = 2.8 bu/acre bu/acre

  42. Simulated CEW Feeding (Blister)Steckel et al.

  43. Tennessee - Corn Isolines ComparisonsImpact of New Bt Technologies (VT3 Pro, SmartStax, Viptera) * Average of 3 (2008) or 2 hybrids (2009) that were VT Pro or SmartStax

  44. Yield of Selected Seed Trt’s and In-Furrow Combinations (MS, Catchot)

  45. Non-Bt Corn Insecticide TestModerate infestations of SWCB (Application July 16, 2008) a b b c a a b b Planted May 1

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