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-Bt corn
Primarily for corn borers
Bt corn technologies
There are just so many options

3. Corn Seed Treatments (company offerings)
DeKalb (Monsanto)
Pioneer
Syngenta
Acceleron
Acceleron + Poncho/VOTiVO
PPST 250
PPST Poncho/VOTiVO
CruiserMaxx Corn
Avicta Complete Corn
Clothianidin*
(250 Rate)
Clothianidin
(500 or 1250 Rate)
Thiamethoxam*
(250)
Thiamethoxam
(500 Rate)
Trifloxystrobin*
Azoxystrobin*
(1250)
Azoxystrobin
Metalaxyl*
Fludioxonil*
Fludioxonil
Ipconazole*
Mefenoxam*
Mefenoxam
Bacillus firmus
(VOTiVO)
Thiabendazole*
Thiabendazole
Abamectin
INSECT
DISEASE
NEMATODE
* Base treatments if premium seed treatments are not requested

4. Relative Efficacy of Corn IST
Trade Name
Billbugs
White grubs
Wire-worms
Seedcorn maggot
Cut-worms
Sugar-cane beetle
Stink bugs
Chinch bugs
Southern corn rootworm
Poncho 250, Acceleron
P, NL F G E
P - F
F +
Poncho 500, Acceleron with Poncho Votivo
F - G
G - E
Poncho 1250, Acceleron
Cruiser Extreme 250 P
G - E, NL
Cruiser Extreme 500, Avicta Complete
Cruiser Extreme 1250
P = poor F = fair G = good E = excellent NL = not labeled

5. Corn At-planting Insecticides, Trial 1 2013, Tennessee

6. Corn At-planting Insecticides, Trial 2 2013, Tennessee

7. Capture LFR In-furrow Trial Starkville, 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 Yield SWCB infested, non-Bt plants (Steckel and Stewart)
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 Tasseling and later 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 Trapping Moths/Trap/Week (Henry Co, TN, 2012)
Spray
Scout / Spray
Action Thresholds 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 Selection Refer 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 Bt Corn 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)
Trademarked Brands
Corn borers
Cutworm
Corn earworm
Fall armyworm
WCRW
YieldGard CB
Excellent
Poor
Fair
None
Herculex
Good
Herculex XTRA
Agrisure CB/LL
Genuity VT Double Pro (VT2P)
Very Good
Genuity VT Triple Pro (VT3P)
Genuity or Dow AgroSciences SmartStax (GENSS or SSX)
Agrisure Viptera 3110
Agrisure Viptera 3111
Optimum Intrasect
Optimum AcreMax Extra

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: Dunklin New Madrid Pemiscot Scott Stoddard
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-Bt Corn
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. All the Bt lep traits provide near perfect control of SWCB and ECB
SWCB and ECB Injury CM Tunneling per 20 Stalks (TN, 2010) a
P < (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 borers Yield (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 a b c c
Herculex
Optimum Intrasect
Viptera

25. Corn Earworm
The most common ear feeding caterpillar

26. SmartStax Test
SmartStax
(90%)
Non Bt
VT3

27. SmartStax Test
Non Bt
VT3P or SS
(40%)

28. Approximate Reduction in Kernel Damage Compared with Non-Bt Corn (Summarized Across Multiple University Trials, Corn Earworm)
Bt Traits
Range of Reduction (%)
Average Reduction (%)
Herculex and HXX
< 15
YieldGard, VT3, Optimum …
0 - 60 40
VT2Pro, VT3P, SmartStax 75
Viptera (VIP3A)
90 – 99 95

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.)
Early Maturity
Medium Maturity
Full Maturity 1
CB / RW
HX / RW
VT3P 2 CB 3
VT3 HX 4 5
VT2P 6 7
VIP
Non- BT 8 9 10
Non-Bt

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

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

33. Simulated Corn Earworm Injury, Milk Stage Steckel and Stewart, 2011
# Kernels Injured
# Kernels per Ear
Total Wt (g) per Ear
Wt (g) of Individual Kernels
592 a
165 a
0.2791c 30
560 b
162 a bc 60
507 c
149 b ab
120
477 d
143 b a

34. Spraying Corn for Corn Earworm
Foliar applications for ear stage infestations of corn earworm in field corn are not 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 Test 2
No statistically significant differences

38. Infestations are usually worse along field margins.
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 < , LSD(0.05) = 0.094, CV = 61.9
P = , 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 bu/acre bu/acre
P = , LSD(0.05) = 16.7, CV = 6.4
P = , LSD(0.05) = 8.5, CV = 2.8
bu/acre
bu/acre

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

43. Tennessee - Corn Isolines Comparisons Impact of New Bt Technologies (VT3 Pro, SmartStax, Viptera)
Yield (B/A)
Location & Year
Non-Bt
YG or VT3
VT3 Pro or SS
TN – 2007
213
257
242
TN – 2008
207
---- (207)
233 *
TN – 2009
114
150
127 *
TN – 2009 (demo)
144
126
149
194
206
199
TN – 2010 (early)
147
152
TN – 2010 (late)
154
160
Average
167.6
179.7
179.5
Bt11
Viptera
135
163
151
TN – 2011
172
171
* 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 Test Moderate infestations of SWCB (Application July 16, 2008)
Planted May 1