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SITUATION
Corn harvest is in full swing across most of the state after the warm weekend weather. Insect pressure has increased, especially from corn earworm with many locations being placed on 4-day spray intervals. ECB pressure has remained low with the exception of a few northern locations, and fall armyworm appears to be slightly on the rise, but hasn’t exceeded thresholds anywhere. With the prospect of southerly thunderstorms throughout most of the next week, insect pressure is not expected to decrease.
European corn borer: Moth counts were still high in a few northern locations this week, requiring protection of silking corn, though only one location wasn’t already protecting against corn earworm. Counts remained low in most southern fields. Biddeford, Charleston, Levant, Palmyra, Wells and East Corinth were over the threshold of 5 moths in silking corn. Feeding injury from larvae in whorl to tassel stage corn remained low in all locations this week, not exceeding the 15% feeding injury threshold in any locations.
Corn earworm: Continued pressure from corn earworm has resulted in spray recommendations at all but 3 locations. A 4-day spray interval was recommended in Biddeford, Cape Elizabeth, Dayton, Dresden, Levant, one Lewiston location, New Gloucester, Nobleboro, North Berwick, Oxford, and Wells. A 5-day spray interval was recommended for Jefferson, Lewiston, Monmouth, Palmyra, Poland Spring, Sabattus, and Warren. A 6-day spray interval was recommended for fields in Charleston and Livermore Falls. Fields in Farmington and Wales caught single moths, which does not warrant a spray.
Fall armyworm: Moth captures of fall armyworm are increasing. When scouting, a spray is recommended if feeding injury exceeds 15% of plants in a pre-silking field. However, larvae may also move into the ears through the silk channel, behaving similarly to corn earworm. Pheromone trap catches of 3 or more moths per week indicate a spray is needed to protect silking corn, unless it is already under a spray schedule for corn earworm. Two fall armyworm moths were caught at each Cape Elizabeth location, both Dayton locations, and a single moth was caught at each Wells location this week. This is below threshold for silking corn. No feeding damage was found.
Other Pests of Note:
Corn smut is often observed in fields this time of year. This fungus disease is easily recognized by the large galls which form in the ears, tassels, and on leaves. The young galls are silvery-white in color. When the galls mature they rupture into masses of powdery, black spores. This fungus tends to infect plants with a prior injury, perhaps from cultivation or insect feeding. Smut usually affects a few plants in a field and is not considered an economically significant problem. There is no effective fungicide for corn smut.
Sincerely,David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box179 491 College Ave
Monmouth,ME 04259 Orono,ME 04473
207.933.2100 1.800.287.0279
| Location | CEW Moths |
ECB Moths |
FAW Moths |
% ECB Damage |
Recommendations / Comments |
| Biddeford | 36 | 11 | 0 | 2% | 4-day spray interval for all silking corn |
| Cape Elizabeth I | 50 | 0 | 2 | 0% | 4-day spray interval for all silking corn |
| Cape Elizabeth II | 20 | 1 | 2 | 0% | 4-day spray interval for all silking corn |
| Charleston | 3 | 11 | 0 | 3% | 6-day spray interval for all silking corn |
| Dayton I | 14 | 0 | 2 | 1% | 4-day spray interval for all silking corn |
| Dayton II | 8 | 0 | 2 | 0% | 4-day spray interval for all silking corn |
| Dresden | 9 | 0 | 0 | 2% | 4-day spray interval for all silking corn |
| East Corinth | 0 | 6 | 0 | 0% | One spray recommended for ECB on silking corn |
| Farmington | 1 | 1 | 0 | 2% | No spray recommended |
| Jefferson | 7 | 1 | 0 | 4% | 5-day spray interval for all silking corn |
| Levant | 11 | 13 | 0 | 10% | 4-day spray interval for all silking corn |
| Lewiston | 4 | 0 | 0 | 0% | 5-day spray interval for all silking corn |
| Lewiston II | 9 | 0 | 0 | 8% | 4-day spray interval for all silking corn |
| Livermore Falls | 2 | 2 | 0 | 1% | 6-day spray interval for all silking corn |
| Monmouth | 6 | 1 | 0 | 7% | 5-day spray interval for all silking corn |
| New Gloucester | 26 | 0 | 0 | 1% | 4-day spray interval for all silking corn |
| Nobleboro | 14 | 3 | 0 | 5% | 4-day spray interval for all silking corn |
| North Berwick | 15 | 3 | 0 | 6% | 4-day spray interval for all silking corn |
| Oxford | 10 | 0 | 0 | 4% | 4-day spray interval for all silking corn |
| Palmyra | 4 | 5 | 0 | 6% | 5-day spray interval for all silking corn |
| Poland Spring | 5 | 0 | 0 | 6% | 5-day spray interval for all silking corn |
| Sabattus | 7 | 0 | 0 | 9% | 5-day spray interval for all silking corn |
| Wales | 1 | 0 | 0 | 4% | No spray recommended |
| Warren | 7 | 0 | 0 | 8% | 5-day spray interval for all silking corn |
| Wells I | 40 | 0 | 1 | 7% | 4-day spray interval for all silking corn |
| Wells II | 48 | 5 | 1 | 1% | 4-day spray interval for all silking corn |
CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm
Corn Earworm Spray Thresholds for Pheromone Traps
| 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:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/
Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.
Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.
Image Description: Sweet Corn
Image Description: European Corn Borer Larvae on Pre-tassel Stage Corn
Image Description: Corn Earworm
Image Description: Fall Armyworm Eggs on Corn
Image Description: Smut on Corn
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