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Sweet Corn IPM Newsletter No. 6 – August 2, 2013

Sweet Corn IPM Newsletter No. 6 – August 2, 2013

For full page print version, please see link at the bottom. Click on photos to enlarge.


Corn Earworm, Fall Armyworm & European Corn Borer Pressure Remains Light

Weather patterns continue to keep insect pressure fairly light in most locations. Harvest continues to look good, although maturity and supply has been spotty. Keep an eye out for late season diseases, especially corn rust, in younger fields.

European corn borer:  Moth catches in southern Maine were low again this week. Only silking fields in New Gloucester, Charleston and Palmyra were over the threshold of 5 moths per week, but the Charleston site is on a spray schedule for corn earworm, so no additional sprays were required. European corn borer feeding damage was over threshold in a pre-tassel field in Oxford this week. When European corn borer and fall armyworm damage are found in the same field, the damage is combined and the spray threshold is lowered to 12% injury. This week a field in Biddeford exceeded the combined injury level.

Corn earworm:  Moth counts are low in all locations this week and most locations did not require protection. A 5-day spray interval was recommended for Charleston and one site in Dayton. A 6-day spray interval was recommended for silking fields in the other Dayton site, as well as Garland, Sabattus and Warren.

Fall armyworm:  Most sites had few or no fall armyworm moths in pheromone traps this week. The exception was Monmouth, where 5 moths were caught; exceeding the weekly threshold of three for silking corn. This is a late field with no silk yet. Single moths were caught in Biddeford, Dayton and Levant.  Very little fall armyworm feeding damage was found in younger corn fields.

Squash vine borer:  Moth counts were down significantly this week. Squash vine borers were caught in North Berwick, Wells, Dayton, Biddeford and Gray, but the threshold of five moths per week was not exceeded at any of these locations. This pest will likely only have one generation per year in Maine, although a late, partial second generation is possible.

Potato Leafhopper Alert:  Potato leafhopper feeding is showing up in vegetable and berry fields this week. Leafhoppers are small, bullet-shaped insects that feed on plant sap, causing the leaves to become curled, stunted and yellow-streaked. Beans are quite susceptible to the injury, in addition to potatoes and strawberries. The small, whitish leafhoppers adults can be seen flying off the plants when disturbed. The small, (1/16 inch) light green leafhopper nymphs are found on the underside of injured leaves.  Control options are listed in the New England Vegetable Management Guide.

Spotted Wing Drosophila Alert:  Captures of the fruit fly were fairly low this week, indicating that the population has not started its exponential growth yet. Flies were caught in Wells, New Gloucester, Dresden and Bowdoinham. The larvae of these flies can quickly destroy any soft fruit such as raspberries and blueberries. When spotted wing drosophila is found in your area, ripening fruit should be protected with a recommended insecticide. Regular and repeated treatments are usually needed to keep fruit from becoming infested. Visit our Spotted Wing Drosophila blog for more details.


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
207.933.2100                          1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Recommendations / Comments
Auburn 0 0 0 0% No spray recommended
Biddeford 1 1 1 14% One spray recommended for ECB + FAW feeding
Cape Elizabeth I 0 0 0 5% No spray recommended
Cape Elizabeth II 0 6 0 One spray recommended on silking corn for ECB
Charleston 7 17 0 3% 5-day spray interval recommended on all silking corn
Dayton I 3 3 0 0% 6-day spray interval recommended on all silking corn
Dayton II 4 1 1 2% 5-day spray interval recommended on all silking corn
Farmington 0 0 0 0% No spray recommended
Garland 3 3 0 1% 6-day spray interval recommended on all silking corn
Gray 0 4 0 0% No spray recommended
Levant 0 5 1 2% One spray recommended on silking corn for ECB
Lewiston 0 1 0 7% No spray recommended
Livermore Falls 0 0 0 No spray recommended
Monmouth 0 3 5 5% No spray recommended (no silking corn)
New Gloucester 1 12 0 0% One spray recommended on silking corn for ECB
No. Berwick 0 0 0 0% No spray recommended
Oxford 0 0 0 19% One spray recommended for ECB feeding
Palmyra 0 18 0 6% One spray recommended on silking corn for ECB
Sabattus 2 5 0 3% 6-day spray interval recommended on all silking corn
Wales 0 1 0 0% No spray recommended
Warren 2 1 0 7% 6-day spray interval recommended on all silking corn
Wells I 0 0 0 4% 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.

IPM Web Pages:

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: European Corn Borer Larva on Ear

Image Description: Corn Earworm Feeding on Corn

Image Description: Potato Leafhopper

Image Description: Male and Female Spotted Wing Drosophila Flies


University of Maine Cooperative Extension

Contact Information

Cooperative Extension at Highmoor Farm
52 U.S. Route 202
Monmouth, Maine 04259-0179
Phone: 207.933.2100
The University of Maine
Orono, Maine 04469
A Member of the University of Maine System