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EARLY CORN HARVEST UNDERWAY
Pest Pressure Remains Moderate for Most Locations
Hot weather and adequate moisture have provided good growing conditions for corn. Early harvest is underway in southern Maine and many fields are now silking, meaning they are now more susceptible to all of the major corn pests. However, in spite of a recent spate of storm fronts from the west, pest numbers have remained relatively moderate in most locations.
European corn borer: With the exception of two northern sites, moth counts were very low this week. Most sites had no moths in the traps. However, silking fields in Levant and Palmyra were over the threshold of 5 moths per week in silking corn. The Levant site was also on a spray regime for corn earworm, so no additional spray was recommended. European corn borer feeding damage was over threshold in pre-tassel to tasseling fields only at our Biddeford site this week.
Corn earworm: While corn earworm was widely distributed throughout our sites this week, moth counts were moderate. However, many later planted fields are now coming into silk and will need to be protected. A 6-day spray interval was recommended for corn earworm on silking fields in North Berwick, Wells, Biddeford, Cape Elizabeth, Bowdoinham, Gray, Farmington, one Lewiston site and Charleston. A 5-day spray interval was recommended for one Dayton site and one Lewiston site, Sabattus, Warren, Nobleboro and Levant.
Fall armyworm: Moth counts were higher in a few locations this week. Fields in Cape Elizabeth, Garland, Lewiston, Monmouth and Nobleboro exceeded the threshold of 3 moths per week in silking corn. However, only the Garland site was not also on a spray regime for corn earworm. Feeding damage on plants was noted this week in fields in Biddeford, Cape Elizabeth and Sabattus. Although not yet over threshold on it’s own, when combined with European corn borer damage the total feeding exceeded the 15% threshold in Biddeford.
Squash vine borer moths were caught in pheromone traps in Biddeford, Oxford and Wells this week. The threshold of five moths per week was exceeded only at the Wells site. Vine borers threaten summer squash, winter squash and pumpkins. See the New England Vegetable Management Guide for control options.
Potato leafhopper alert: We are seeing signs of potato leafhopper in vegetable and strawberry fields this week. These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked. Beans are often the first crop to show symptoms, but other crops are also susceptible, including potatoes and strawberries. To scout for leafhoppers, brush the leaves of the plants with your hand. The small, whitish adults can be seen flying off the plant. Look for small, light green leafhopper nymphs on the underside of injured leaves. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Controls for potato leafhoppers are listed in the New England Vegetable Management Guide.
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box 179 491 College Avenue
Monmouth, ME 04259 Orono, ME 04473
Sweet Corn IPM Weekly Scouting Summary
|Recommendations / Comments|
|Biddeford||2||0||2||17%||6-day spray interval recommended on all silking corn|
|Bowdoinham||3||0||1||4%||6-day spray interval recommended on all silking corn|
|Cape Elizabeth I||3||0||3||6%||6-day spray interval recommended on all silking corn|
|Cape Elizabeth II||3||0||12||2%||6-day spray interval recommended on all silking corn|
|Charleston||2||0||0||6-day spray interval recommended on all silking corn|
|Dayton I||0||0||0||No spray recommended|
|Dayton II||6||0||0||12%||5-day spray interval recommended on all silking corn|
|Farmington||2||0||2||1%||6-day spray interval recommended on all silking corn|
|Garland||1||0||5||0%||One spray recommended for FAW on silking corn|
|Gray||3||0||0||6-day spray interval recommended on all silking corn|
|Levant||4||6||0||2%||5-day spray interval recommended on all silking corn|
|Lewiston I||5||0||10||5%||5-day spray interval recommended on all silking corn|
|Lewiston II||3||0||2||6-day spray interval recommended on all silking corn|
|Livermore Falls||0||0||0||0%||No spray recommended|
|Monmouth||1||2||11||No spray recommended (no silking corn)|
|Nobleboro||5||0||3||1%||5-day spray interval recommended on all silking corn|
|No. Berwick||2||0||0||6-day spray interval recommended on all silking corn|
|Oxford||1||0||1||2%||No spray recommended|
|Palmyra||1||19||1||3%||One spray recommended for ECB on silking corn|
|Sabattus||5||2||0||13%||5-day spray interval recommended on all silking corn|
|Wales||1||0||2||0%||No spray recommended|
|Warren||7||0||2||0%||5-day spray interval recommended on all silking corn|
|Wells I||3||0||0||3%||6-day spray interval recommended on all silking corn|
|Wells II||1||0||0||0%||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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