Sweet Corn IPM Newsletter No. 10 — August 16, 2024
HIGH CORN EARWORM NUMBERS CONTINUE
Fall Armyworm Also Threatens Corn in Many Fields
SITUATION
Pest pressure remains high for silking corn this week with high numbers both of corn earworm and fall armyworm found most fields. Growers should remain on tight spray intervals in silking fields to keep ears from being infested.
European corn borer: Moth captures continue to be very low this week. No sites were over the spray threshold for moths in silking corn. Very little larval feeding damage was found in pre-silking corn, and no sites were over threshold.
Corn earworm: Moth captures continue to be high this week, likely bolstered by the remains of the recent tropical storm coming through the state. Growers should maintain a tight spray schedule on fresh silking corn to prevent infestation. A 6-day spray interval for silking corn was recommended in Farmington and Palmyra; a 5-day spray interval was recommended in Garland; a 4-day spray interval was recommended for Auburn, Biddeford, Cape Elizabeth, Gray, Lewiston, Monmouth, Oxford, Wayne and Wells; a 3-day spray schedule was recommended in Bowdoinham and Dayton.
Fall armyworm: Moth counts in pheromone traps were generally higher this week. Auburn, Biddeford, Bowdoinham, Cape Elizabeth, Dayton, Farmington, Gray, Lewiston, Monmouth, Oxford, Wayne and one site in Wells were over the three-moth threshold for silking corn in pheromone traps, but all sites are presently under a spray interval for corn earworm, which should provide control of fall armyworm. Larval feeding damage was moderate in most pre-silking corn, but sites in Biddeford, Bowdoinham and Gray were over threshold of 12-15% of plants with fresh injury.
Western Bean Cutworm: Captures of moths in pheromone traps were very low at nearly all locations this week, ranging from zero to 11 moths in a trap. Sprays for corn earworm and fall armyworm should protect silking corn from western bean cutworm, and no additional controls were recommended.
Squash vine borer: Moth numbers in pheromone traps were below threshold at all locations this week, and no sprays were recommended.
Plectosporium blight: Symptoms of Plectosporium have been found in many pumpkin and squash fields over the past two weeks. This fungus disease causes white flecking on the surface of the fruit and leaves, leading to collapse of the plants and fruit rot. See the New England Vegetable Management Guide for details. The fungicides Quadris Top®, Merivon®, Cabrio® and Flint® are labeled for use on pumpkins and squash to control Plectosporium.
Save the Date!
The New England Vegetable & Fruit Conference will be held in Manchester, NH December 17, 18, 19, 2024. Program and registration information will be coming soon. Visit the website: http://www.newenglandvfc.org/
Sincerely,
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm
P.O. Box 179
52 U.S. Route 202
Monmouth, ME 04259
207.933.2100
UMaine Extension Diagnostic Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473
1.800.287.0279
| Location | CEW Moths | ECB Moths | FAW Moths | WBC Moths | %Feeding Damage | Recommendations / Comments |
|---|---|---|---|---|---|---|
| Auburn | 32 | 0 | 11 | 0 | 4-day spray interval for silking corn | |
| Biddeford | 19 | 0 | 14 | 0 | 17% | 4-day spray interval for silking corn |
| Bowdoinham | 93 | 1 | 18 | 2 | 20% | 3-day spray interval for silking corn |
| Cape Elizabeth | 90 | 0 | 11 | 1 | 12% | 4-day spray interval for silking corn |
| Dayton | 103 | 0 | 31 | 3 | 0% | 3-day spray interval for silking corn |
| Farmington | 3 | 2 | 4 | 6 | 6-day spray interval for silking corn | |
| Garland | 5 | 1 | 1 | 7% | 5-day spray interval for silking corn | |
| Gray | 26 | 0 | 13 | 0 | 15% | 4-day spray interval for silking corn |
| Lewiston | 75 | 0 | 11 | 0 | 4-day spray interval for silking corn | |
| Monmouth | 35 | 0 | 41 | 3 | 4-day spray interval for silking corn | |
| Oxford | 29 | 3 | 32 | 6 | 9% | 4-day spray interval for silking corn |
| Palmyra | 3 | 1 | 1 | 6-day spray interval for silking corn | ||
| Wayne | 8 | 0 | 24 | 11 | 1% | 4-day spray interval for silking corn |
| Wells I | 68 | 0 | 2 | 0 | 3% | 4-day spray interval for silking corn |
| Wells II | 18 | 0 | 6 | 1 | 1% | 4-day spray interval for silking corn |
CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm
CBW: Western bean cutworm
| Moths caught per week | Moths caught per night | Spray Interval |
|---|---|---|
| 0.0 to 1.4 | 0.0 to 0.2 | No spray |
| 1.5 to 3.5 | 0.3 to 0.5 | Spray every 6 days |
| 3.6 to 7.0 | 0.6 to 1.0 | Spray every 5 days |
| 7.1 to 91 | 1.1 to 13.0 | Spray every 4 days |
| More than 91 | More than 13 | Spray every 3 days |
Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.
European Corn Borer Thresholds
Whorl stage: 30% or more of plants scouted show injury.
Pre-tassel-silk: 15% or more of plants scouted show injury.
Silk: 5 or more moths caught in pheromone traps in one week.
IPM Web Pages:
Explore Integrated Pest Management in Maine — UMaine
Integrated Pest Management Data Visualization Tool — Penn State
Integrated Pest Management — UMass Amherst
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