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CORN PEST ACTIVITY REMAINS LOW IN MOST LOCATIONS
Western Bean Cutworm Found in Maine Corn Fields
Early harvest is getting into full swing and corn quality is looking good, although ear size has been a bit small due to dry conditions in some areas. Moth counts continue to be very low for this time of year, but nobody is complaining.
European corn borer: Moth counts were very low in southern locations this week, but some northern sites continue to have enough moths flying to warrant protection of silking corn. Three sites, Charleston, Levant and East Corinth were over the threshold of 5 moths in silking corn. Feeding injury from larvae in whorl to tassel stage corn was also less prevalent this week, only exceeding the 15% feeding injury threshold in Biddeford, Jefferson, Poland Spring and Sabattus.
Corn earworm: There was a slight increase in moth activity in a few locations this week. A 6-day spray interval for fresh silking corn was recommended for fields in Nobleboro, North Berwick, Palmyra, and Poland Spring. Three locations had only single moths, which don’t warrant a spray. Most locations had no moths.
Fall armyworm: No fall armyworm moths were caught this week and no feeding damage was found in the field.
Western bean cutworm: A new corn pest for Maine?
We set out pheromone traps for western bean cutworm in cornfields this spring, based on reports that this insect is becoming a problem in corn in the upper Midwest and mid-Atlantic regions. We have caught a few moths in Wells, Cape Elizabeth and New Gloucester over the past couple weeks, and we’re now evaluating what level of risk these present. The larvae of western bean cutworm will feed on corn plants and move into the ears either through the silk channel or through the husks. Unlike corn earworm, they are not cannibalistic; so many larvae may be found in a single ear, feeding on the kernels. The threshold for feeding injury on plants is 8%. There isn’t an established threshold for moths laying eggs in silking corn yet, but plants that are already on a spray program for corn earworm should also be protected from western bean cutworm.
Spotted wing drosophila update: We have found this “new” fruit fly in more locations and in higher numbers this week, threatening raspberries, blueberries and any other soft fruit that is available. We have now caught this fly in traps in Limington, Sanford, New Gloucester, Mechanic Falls, Wales, Litchfield, Fayette, Thorndike, and Warren. Growers should be on the alert and look for fruit flies on their fruit and symptoms of premature fruit decay. At this point, keeping fields free of overripe fruit and weekly insecticide sprays appear to be keeping this pest in check. However more frequent sprays may become necessary as pest populations increase. There is a good fact sheet on management of spotted wing drosophila on the Penn State Extension website.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm PestManagement Office
P.O. Box179 491 College Ave
Monmouth,ME 04259 Orono,ME 04473
Sweet Corn IPM Weekly Scouting Summary
|Recommendations / Comments|
|Biddeford||0||0||0||30%||One spray recommended for ECB feeding|
|Cape Elizabeth I||0||0||0||6%||No spray recommended|
|Cape Elizabeth II||0||0||0||10%||No spray recommended|
|Charleston||0||5||0||1%||One spray recommended for ECB on silking corn|
|Dayton I||0||0||0||0%||No spray recommended|
|Dayton II||1||0||0||0%||No spray recommended|
|Dresden||0||0||0||9%||No spray recommended|
|East Corinth||0||6||0||0%||One spray recommended for ECB on silking corn|
|Farmington||0||1||0||3%||No spray recommended|
|Jefferson||0||0||0||19%||One spray recommended for ECB feeding|
|Levant||0||5||0||5%||One spray recommended for ECB on silking corn|
|Lewiston||0||0||3%||No spray recommended|
|Lewiston II||0||0||0||13%||No spray recommended|
|Livermore Falls||1||0||0||1%||No spray recommended|
|Monmouth||0||1||0||0%||No spray recommended|
|New Gloucester||0||0||0||2%||No spray recommended|
|Nobleboro||2||0||0||0%||6-day spray interval for all silking corn|
|North Berwick||2||0||0||0%||6-day spray interval for all silking corn|
|Oxford||0||1||0||5%||No spray recommended|
|Palmyra||2||3||0||3%||6-day spray interval for all silking corn|
|Poland Spring||2||0||0||21%||6-day spray interval for all silking corn|
|Sabattus||0||0||0||23%||One spray recommended for ECB feeding|
|Wales||0||0||0||0%||No spray recommended|
|Warren||0||0||0||0%||No spray recommended|
|Wells I||1||0||0||0%||No spray recommended|
|Wells II||0||1||0||6%||No spray recommended|
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.
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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.