Sweet Corn IPM Newsletter No. 13 — September 6, 2024
MODERATE PEST PRESSURE FOR LATE SEASON CORN
Fall Armyworm Counts Higher in Most Locations
SITUATION
Sweet corn season is winding down for most farms. Cool nights and favorable weather patterns continued to keep pest levels at low to moderate levels this week. Corn earworm and fall armyworm are the primary issue for any silking corn remaining. European corn borer and western bean cutworms have not been present in most locations. Next week will be the last scheduled issue of the Sweet Corn IPM Newsletter for the 2024 season.
European corn borer: Moths were only found at sites in Monmouth and Dayton this week, but were well below the control threshold.
Corn earworm: Moth activity continued to be low to moderate this week as cooler night temperatures and fair weather have slowed activity and reduced incoming moths from the south. More sites no longer have corn in the fresh silk stage, so earworm is no longer a threat. A 6-day spray interval for silking corn was recommended in Bowdoinham and Oxford; a 5-day spray interval was recommended in Biddeford and Wayne; a 4-day spray interval was recommended for Cape Elizabeth and Corinth.
Fall armyworm: Moth counts in pheromone traps were generally high enough to recommend continued protection of silking corn. Biddeford, Bowdoinham, Cape Elizabeth, Corinth, Dayton, Gray, Monmouth, Wayne and one site in Wells were over the three-moth threshold for silking corn in pheromone traps. Only Oxford and the Wells location were not under a spray interval for corn earworm, so protective sprays were recommended.
Western Bean Cutworm: No moths were caught in any of our pheromone traps this week.
After the crop is harvested: Plowing down corn stalks after the season can help reduce overwintering European corn borer populations, but the resulting open ground may also lead to significant soil erosion. Plant winter rye after harvest (90 lb./acre) to generate a vegetative cover to prevent erosion. Applying manure in the fall can also be useful for soil building and fertility but it should be applied and incorporated before the soil freezes, or by December 1st at the latest. Soil tests will help determine appropriate rates. For example, dairy manure applied at a rate of 20 tons per acre may supply nearly enough nitrogen for a crop of corn. Be sure to follow all food safety precautions for manure applications when applying to a field intended for growing a crop intended for human consumption.
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 |
|---|---|---|---|---|---|---|
| Biddeford | 5 | 0 | 15 | 0 | 5-day spray interval for silking corn | |
| Bowdoinham | 2 | 0 | 14 | 0 | 6-day spray interval for silking corn | |
| Cape Elizabeth | 19 | 0 | 44 | 0 | 4-day spray interval for silking corn | |
| Corinth | 9 | 0 | 15 | 4-day spray interval for silking corn | ||
| Dayton | 1 | 1 | 12 | 0 | One spray for FAW on silking corn | |
| Gray | 3 | 0 | 14 | 0 | 6-day spray interval for silking corn | |
| Monmouth | 0 | 2 | 20 | 0 | One spray for FAW on silking corn | |
| Oxford | 3 | 0 | 1 | 0 | 6-day spray interval for silking corn | |
| Wayne | 5 | 0 | 14 | 0 | 5-day spray interval for silking corn | |
| Wells I | 0 | 0 | 4 | 0 | One spray for FAW on silking corn | |
| Wells II | 0 | 0 | 1 | 0 | No spray recommended |
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 — UMass Amherst
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