For full page print version, please see link at the bottom. Click on photos to enlarge.
With continued southerly weather and thunderstorms passing through the state, insect pressure has remained high, mostly due to corn earworm. At this point, every location is on at least a 4-day spray interval, with some locations on 3-day intervals. For many growers, the youngest corn has reached the silking stage as the corn season begins to come to a close. Warm weather will continue to help corn mature rapidly and insect pressure will likely remain relatively high.
European corn borer: Insect counts have decreased, with only two locations over the 5-moth threshold: Biddeford and Charleston. Feeding damage from ECB in whorl to tassel stage corn has been present in all fields scouted, but exceeded the 15% threshold in only two locations (Biddeford and Sabattus) when fall armyworm damage was added to the total.
Corn earworm: Moth counts remain high in all locations, putting very high pressure on all silking corn. A 3-day spray interval for fresh silking corn was recommended for Biddeford, one Cape Elizabeth location, Dayton, one Lewiston location, and Sabattus. A 4-day spray interval was recommended in one Cape Elizabeth location, Charleston, East Corinth, Farmington, Jefferson, Levant, Livermore Falls, Monmouth, New Gloucester, Nobleboro, Oxford, Palmyra, Poland Spring, Wales, Warren, and Wells. No locations had a moth count low enough for a 5- or 6-day spray interval.
Fall armyworm: We continue to find feeding damage in southern fields, but only Biddeford and Sabattus were over the threshold when combined with ECB feeding damage. Moth captures remain low for this time of year, with only one Cape Elizabeth location exceeding the spray threshold of 3 moths in silking corn; but the field is already under a spray schedule for corn earworm so no additional sprays should be needed. Two fall armyworm moths were caught at Monmouth and Sabattus, and a single moth was caught in Biddeford, Cape Elizabeth, and one Dayton location this week, below threshold for silking corn. Fall armyworm feeding damage was also found in Cape Elizabeth, New Gloucester, and North Berwick, but was below the 15% threshold.
Other Pests of Note
Aphids: Some fields are starting to show infestations of aphids on the tassels, silks and husks. While their feeding is not usually a significant problem, the presence of aphids and the sooty mold that develops on the husks as a result of their waste (called honeydew) is often objectionable to customers. Sprays, other than the Bt’s or spinosad products, that are used to control the major corn pests also offer control of aphids as well, including Asana®, Capture®, Warrior® and Lannate®.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box 179 491 College Ave
Monmouth, ME 04259 Orono, ME 04473
|Recommendations / Comments|
|Biddeford||95||10||1||15%||3-day spray interval for all silking corn|
|Cape Elizabeth I||162||3||1||All Silk||3-day spray interval for all silking corn|
|Cape Elizabeth II||85||4||11||6%||4-day spray interval for all silking corn|
|Charleston||11||5||0||4%||4-day spray interval for all silking corn|
|Dayton I||118||1||0||All Silk||3-day spray interval for all silking corn|
|Dayton II||113||0||1||All Silk||3-day spray interval for all silking corn|
|East Corinth||21||0||0||2%||4-day spray interval for all silking corn|
|Farmington||14||0||0||All Silk||4-day spray interval for all silking corn|
|Jefferson||44||0||0||All Silk||4-day spray interval for all silking corn|
|Levant||54||3||0||6%||4-day spray interval for all silking corn|
|Lewiston||152||0||0||All Silk||3-day spray interval for all silking corn|
|Livermore Falls||29||0||0||3%||4-day spray interval for all silking corn|
|Monmouth||71||0||2||All Silk||4-day spray interval for all silking corn|
|New Gloucester||30||0||0||9%||4-day spray interval for all silking corn|
|Nobleboro||20||2||0||1%||4-day spray interval for all silking corn|
|Oxford||50||0||0||All Silk||4-day spray interval for all silking corn|
|Palmyra||8||0||0||4%||4-day spray interval for all silking corn|
|Poland Spring||29||1||0||All Silk||4-day spray interval for all silking corn|
|Sabattus||145||2||2||16%||3-day spray interval for all silking corn|
|Wales||16||0||0||3%||4-day spray interval for all silking corn|
|Warren||83||2||0||All Silk||4-day spray interval for all silking corn|
|Wells I||50||0||0||All Silk||4-day spray interval for all silking corn|
|Wells II||89||3||0||All Silk||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
|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.
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: Print Friendly
Image Description: Sweet Corn
Image Description: European Corn Borer Larvae on Ear
Image Description: Corn Earworm Feeding on Corn
Image Description: Fall Armyworm Injury on Corn Leaves
Image Description: Aphids on Corn