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Recent relatively cool nights indicate a shift in the weather pattern and have resulted in a dramatic drop in corn earworm captures this week. However, populations are still high enough to keep all silking fields on a regular spray schedule. As we approach Labor Day and the season starts to wind down, we have very little pressure from either fall armyworm or European corn borer. Hot weather predicted for the remainder of the week will push remaining corn maturity along rapidly. Remnants of hurricane Isaac may visit Maine next week and could bring with it a new flush of earworm and armyworm.
European corn borer: Moth counts are very low this week with no sites exceeding the 5-moth threshold for silking corn. Feeding damage was also low, with only the North Berwick site exceeding the 15% threshold when it was combined with fall armyworm damage.
Corn earworm: Moth counts were significantly lower in all locations this week, but pressure still remains moderate to high for many locations. A 3-day spray interval for fresh silking corn was recommended only for North Berwick. A 4-day spray interval was recommended for Biddeford, one Cape Elizabeth location, Dayton, Dresden, East Corinth, Levant, Lewiston, Monmouth, Wales, Wayne and one Wells location. A 5-day spray interval was recommended for one Cape Elizabeth location, New Gloucester, Nobleboro, Oxford, and one Wells location. A 6-day spray interval was recommended for Charleston, Jefferson, Palmyra, Poland Spring, and Warren.
Fall armyworm: We continue to find light feeding damage in some fields, but only North Berwick was over the threshold when combined with ECB feeding damage. Moth captures continue to be very low for this time of year, with no sites exceeding the spray threshold of 3 moths in silking corn. Two fall armyworm moths were caught at Cape Elizabeth, and one Lewiston location, and single moths were caught in Biddeford, Cape Elizabeth, Dresden, East Corinth, New Gloucester, and Warren. Fall armyworm feeding damage was found in Biddeford, Cape Elizabeth and New Gloucester, but was below the 15% threshold. Most remaining fields are silking and under a spray schedule for corn earworm, so field scouting is not necessary.
Spotted Wing Drosophila Update:
Over the last week spotted wing drosophila numbers have risen significantly. Flies are now at their highest levels of the season. We have also found drosophila maggots infesting blueberry, raspberry, blackberry, elderberry, grape and peach fruit this week. For those with late fruit crops still to harvest, protection is necessary to prevent infestation by spotted wing drosophila. Up to this point weekly applications of an allowed insecticide have been adequate, but reports from the field suggest that more frequent applications may be necessary to keep fruit free from maggots. Growers in southern states have found that a 3 to 5-day spray schedule was needed to prevent infestation.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box179 491 College Ave
Monmouth,ME 04259 Orono,ME 04473
|%Feeding Damage||Recommendations / Comments|
|Biddeford||8||1||1||6%||4-day spray interval for all silking corn|
|Cape Elizabeth I||9||0||2||All silking||4-day spray interval for all silking corn|
|Cape Elizabeth II||7||0||1||5%||5-day spray interval for all silking corn|
|Charleston||2||1||0||1%||6-day spray interval for all silking corn|
|Dayton I||33||0||0||All silking||4-day spray interval for all silking corn|
|Dayton II||15||0||0||All silking||4-day spray interval for all silking corn|
|Dresden||32||0||1||All silking||4-day spray interval for all silking corn|
|East Corinth||16||0||1||0%||4-day spray interval for all silking corn|
|Jefferson||3||0||0||All silking||6-day spray interval for all silking corn|
|Levant||11||0||0||2%||4-day spray interval for all silking corn|
|Lewiston I||47||0||2||All silking||4-day spray interval for all silking corn|
|Lewiston II||11||1||0||0%||4-day spray interval for all silking corn|
|Monmouth||40||0||0||All silking||4-day spray interval for all silking corn|
|New Gloucester||5||0||1||2%||5-day spray interval for all silking corn|
|Nobleboro||5||0||0||All silking||5-day spray interval for all silking corn|
|No. Berwick||129||0||0||18%||3-day spray interval for all silking corn|
|Oxford||5||0||0||All silking||5-day spray interval for all silking corn|
|Palmyra||2||0||0||All silking||6-day spray interval for all silking corn|
|Poland Spring||2||0||0||All silking||6-day spray interval for all silking corn|
|Wales||20||0||0||All silking||4-day spray interval for all silking corn|
|Warren||2||0||1||All silking||6-day spray interval for all silking corn|
|Wayne||18||0||0||All silking||4-day spray interval for all silking corn|
|Wells I||9||0||0||All silking||4-day spray interval for all silking corn|
|Wells II||6||1||0||All silking||5-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.
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.
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Image Description: Sweet Corn
Image Description: Corn Earworm Larvae
Image Description: Fall Armyworm on Corn Silk
Image Description: Spotted Wing Drosophila Larva in Blueberry
Image Description: Spotted Wing Drosophila Larvae in Raspberry