update on corn earworm management in sweet corn rick …...2/15/2019 4 2018 sweet corn insecticide...
TRANSCRIPT
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Update on Corn Earworm Management in Sweet Corn
Rick Foster
Department of Entomology
Purdue University
Corn Earworms
• Primary pest of sweet corn in the Midwest
• Overwinter at some level in most of Indiana
• Migrate north from southern locations; migration can occur any time depending on weather patterns
• First generation (June) is usually fairly small
• Second generation (August) is usually very large
• Sweet corn harvested in late August and September is usually severely attacked by corn earworms
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Corn Earworm Biology
• Females prefer to lay eggs singly on green silks
• Eggs hatch in about 3 days, depending on temperatures
• When eggs hatch, larvae crawl down silk into the ear tip
• Larvae do little or no feeding until they are inside the tip of the ear
• Adult activity can be measured with pheromone traps
General Management Strategy
• A contact insecticide must be present on the silk between the egg and the tip of the ear prior to egg hatch
• Problem is compounded by the growth of silks (1 inch per day) so that each day there is unprotected silks
• Because of silk growth, multiple applications are required
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What Determines the Level of ControlYou Will Receive?
• Correct insecticide
• Correct timing
• Correct placement
Correct Insecticide2017 Insecticide Trial Results
Insecticide Rate per Acre % Clean Ears Damaged Kernels/Ear
Earworms/ Ear
Untreated ‐‐‐ 7.7 b 24.0 a 1.07 a
Coragen 5 fl. oz. 85.5 a 1.4 b 0.13 b
Radiant 6 fl. oz. 83.0 a 2.0 b 0.17 b
Mustang Maxx 4 fl. oz. 75.9 a 4.0 b 0.28 b
Warrior 1.92 fl. oz 73.0 a 4.4 b 0.28 b
Entrust 2 oz. 66.7 a 5.3 b 0.34 b
Helicovex 1.25 fl. oz. 27.0 b 16.5 a 0.84 a
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2018 Sweet Corn Insecticide TrialInsecticide Rate/Acre Application Dates Damaged
Kernels/Ear% Clean Ears
Untreated ‐‐‐‐‐ ‐‐‐‐‐ 10.5 A 3 D
CoragenRadiant
5 fl. oz.6 fl. oz.
A B CD E
3.4 BC 31 ABC
Radiant 6 fl. oz. A B C D E 2.9 BC 40 ABC
Warrior 1.92 fl. oz. A B C D E 5.4 B 30 ABC
CoragenWarrior
5 fl. oz.1.92 fl.oz.
A B CD E
3.0 BC 34 ABC
CoragenWarriorRadiant
5 fl. oz.1.92 fl. oz.6 fl. oz.
A B C A B C D E
D E
1.9 BC 56 A
CoragenHelicovex
5 fl. oz.1.25 fl. oz.
A B CD E
1.5 C 57 A
CoragenHelicovexWarrior
5 fl. oz.1.25 fl. oz.1.92 fl. oz.
A C EB DB D
2.3 BC 48 A B
P>F 0.0001 0.0001
Decision Rules/Correct Timing• Insecticide should be applied if:
• Green silks are present• At least one moth per night is being caught in pheromone traps for early and late plantings
• At least 10 moths per night are being caught in pheromone traps for plantings that are silking at the same time as the surrounding dent corn
• Intervals between sprays will vary between 2 and 5 days depending on trap catch and temperatures
• Applications can cease when most of the silks are brown
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Correct Placement
•What is the best way to get insecticide on the silks?
•Choices:• Boom sprayer• Boom sprayer with drop nozzles• Airblast sprayer• Airplane• Helicopter• Backpack sprayer
2017 Sprayer Type Experiment
• Obsession sweet corn was planted on July 7
• Plots were 8 rows by 30 feet with four replications
• Treatments were:• Untreated control• Boom sprayer with drop nozzles
• Boom sprayer with no drop nozzles
• Airblast sprayer
• Applications were made on August 25, 28, 31, September 5 and 8.
• Water sensitive cards placed on silks to measure coverage
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2017 Sprayer Type Experiment
• At harvest (Sept. 18‐19), 25 ears from each of rows 3 and 6 were harvested from the untreated control, boom with drops, and boom only plots.
• 25 ears were harvested from each of the 8 rows of the airblast plots
Boom Sprayer with Drop Nozzles
• Boom covered four rows with one nozzle over the top of each row and two drop nozzles for each row, angled slightly upward
• 12 total nozzles for 4 rows
• 26.7 gallons per acre
• 30 psi
• TXVS‐12 conejet nozzles
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Boom Sprayer
• 9 nozzles spaced every 15 inches so there was one nozzle over each row and one offset 15 inches from each row
• 23.1 gallons per acre
• 30 psi
• TXVS‐12 conejet nozzles
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Airblast Sprayer
• John Bean 458T
• Pressure: 350 psi
• Ground speed: 4.5 mph
• GPA: 40 at 20 foot swath
• Nozzles: Turn over discs (John Bean)
• Tip: Ceramic whirl plates and discs
• Nozzles and air baffles oriented straight into the crop
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Coverage: Boom Sprayer with Drops
1 2 3 4
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Coverage: Boom Sprayer No Drops
1 2 3 4
Coverage: Airblast Rep 1
1 2 3 4
5 6 7 8
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2017 Spray Coverage
Sprayer Type Coverage
Boom with drops 207 a
Boom no drops 150 ab
Airblast 47 b
2017 Spray Coverage by Row with Airblast
0
20
40
60
80
100
120
140
1 2 3 4 5 6 7 8
Row
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2017 Earworm Control
Treatment Percentage Clean Ears Damaged Kernels/Ear Earworms/Ear
Untreated 50.5 9.2 a 0.58 a
Boom with Drops 89.4 0.8 b 0.08 b
Boom with No Drops 82.0 1.9 b 0.18 ab
Airblast 76.6 2.7 b 0.25 ab
2017 Airblast Sprayer: Earworm Control by Row
Row Percentage Clean Ears Damaged Kernels/Ear Earworms/Ear
1 99 a 0.2 a 0.01 a
2 100 a 0.0 a 0.00 a
3 96 a 0.4 a 0.04 a
4 92 ab 0.6 ab 0.06 a
5 70 bc 3.5 b 0.34 b
6 62 cd 4.7 b 0.40 bc
7 52 cd 5.8 b 0.50 bc
8 42 d 6.3 b 0.63 c
Boom with Drops 89.4 0.8 0.08
Untreated 50.5 9.2 0.58
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2018 Sprayer Type Experiment
• Obsession sweet corn was planted on July 2• Plots were 8 rows by 30 feet with four replications• Treatments were:
• Untreated control• Boom sprayer with drop nozzles• Boom sprayer with no drop nozzles• Airblast sprayer• Cannon airblast sprayer
• Applications were made on August 22, 24, 27, 29, and 31.
• Water sensitive cards placed on silks to measure coverage
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Coverage: Cannon Rep 1
1 2 3 4
5 6 7 8
2018 Spray Coverage
Sprayer Type Coverage
Boom with drops 207 ab
Boom no drops 157 ab
Airblast 103 b
Cannon 347 a
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2018 Spray Coverage By RowBlue = Cannon Red = Airblast
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1 2 3 4 5 6 7 8
2018 Earworm Control
Treatment Percentage Clean Ears Damaged Kernels/Ear Earworms/Ear
Untreated 11.5 C 12.0 A 0.42 A
Boom with No Drops 40.5 AB 3.6 BC 0.17 BC
Boom with Drops 56.0 A 1.9 C 0.09 C
Airblast 40.0 B 5.0 B 0.22 B
Cannon 52.4 A 2.8 C 0.12 C
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2018 Airblast Sprayer: Earworm Control by Row
Row Percentage Clean Ears Damaged Kernels/Ear Earworms/Ear
1 74 A 0.94 C 0.01 D
2 68 A 1.39 C 0.02 D
3 49 AB 1.95 C 0.13 CD
4 39 BC 2.62 BC 0.11 CD
5 26 BC 6.42 AB 0.35 AB
6 30 BC 7.53 A 0.25 BC
7 18 C 9.27 A 0.39 AB
8 16 C 9.91 A 0.46 A
Boom with Drops 56 1.9 0.09
Untreated 11.5 12.0 0.42
2018 Cannon Sprayer: Earworm Control by Row
Row Percentage Clean Ears Damaged Kernels/Ear Earworms/Ear
1 62 1.95 B 0.03 C
2 55 2.26 AB 0.12 ABC
3 52 3.16 AB 0.18 AB
4 49 2.97 AB 0.07 BC
5 53 2.02 B 0.12 ABC
6 58 2.41 AB 0.11 ABC
7 53 2.50 AB 0.11 ABC
8 37 5.38 A 0.24 A
Boom with Drops 56 1.90 0.09
Untreated 11.5 12.0 0.42
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Disclaimer
• For each of the sprayers, there are a number of variables that could be modified that might change the results
Take Home Messages
• In our study, a boom sprayer with drop nozzles provided better earworm control than a boom sprayer without drop nozzles
• In our study, both boom sprayers provided better earworm control than an airblast sprayer over 8 rows
• In our study, an airblast sprayer provided better control than either of the boom sprayers in the first 4 rows
• In our study, an airblast sprayer did not provide acceptable control after more than 4 rows
• The use of water sensitive cards on the silks provided an accurate prediction of the level of earworm control
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Questions?