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Sweet Corn IPM Newsletter No. 7 – August 9, 2013

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Sweet CornSweet Corn IPM Newsletter No. 7 – August 9, 2013

Click on photos to enlarge.


Corn Earworm, Fall Armyworm & European Corn Borer Damage Low

Another week of fairly light insect pressure in most locations this week, thanks to a relatively stable weather pattern. Storm fronts coming across from the Midwest or the South could quickly bring higher moth counts to the state, but for now most farms are enjoying a light spray schedule for this time of the season.

European corn borer: Moth catches were very low across the state this week. No silking fields exceeded the threshold of 5 moths per week. 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 Sabattus exceeded the combined injury level.

Corn earworm: Moth counts continued to be low in all locations this week and many fields required no additional protection. A 5-day spray interval was recommended for one site in Cape Elizabeth, Charleston, one site in Dayton, and New Gloucester. A 6-day spray interval was recommended for silking fields in Biddeford, Garland, and Nobleboro.

European Corn Borer Entry Hole

European Corn Borer Entry Hole, photo by David Handley

Fall Armyworm Eggs on Corn

Fall Armyworm Eggs on Corn, photo by David Handley

Fall armyworm: Most sites have still not seen significant fall armyworm damage this season. Fall armyworm moths were caught only in Biddeford, one Dayton site and in Nobleboro this week. Biddeford and Dayton exceeded the weekly threshold of three moths for silking corn. A single moth was caught in Nobleboro. Our site in Biddeford was the only location where fall armyworm feeding damage on younger corn exceeded the spray threshold.

Squash vine borer: Moth counts continued to drop this week. Squash vine borers were caught in Cape Elizabeth and Dayton, but the threshold of five moths per week was not exceeded at either of these locations.

Plectosporium blight: Symptoms of Plectosporium have also been found in pumpkin fields over the past two weeks. This fungus disease causes white flecking in the surface of the fruit and leaves, leading to collapse of the plants and fruit rot. See the New England Vegetable Management Guide for details. The fungicides Quadris®, Maneb®, Bravo®, Cabrio® and Flint® are labeled for use on pumpkins to control Plectosporium.

Plectosporium blight on pumpkin

Plectosporium blight on pumpkin, photo by Mark Hutton

Male Spotted Wing Drosophila

Male Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted Wing Drosophila Alert: Fruit fly counts were quite variable this week, with some sights catching few or no flies while one had the highest count of the season. Flies were caught in Wells, Cape Elizabeth, Limington, New Gloucester, Gray, Monmouth, Bowdoinham and Corinna. Most traps had one to three flies in them. The exception was the Bowdoinham site, which had over 200 flies for the week. The tiny larvae of these flies can quickly destroy ripening soft fruit such as raspberries and blueberries. Once spotted wing drosophila is found in your area, 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 6% No spray recommended
Biddeford 3 0 5 19% 6-day spray interval recommended on all silking corn
Cape Elizabeth I 0 0 0 3% No spray recommended
Cape Elizabeth II 5 0 0 5-day spray interval recommended on all silking corn
Charleston 4 3 0 0% 5-day spray interval recommended on all silking corn
Dayton I 6 1 6 7% 5-day spray interval recommended on all silking corn
Dayton II 0 1 0 8% No spray recommended
Farmington 0 0 0 0% No spray recommended
Garland 3 0 0 0% 6-day spray interval recommended on all silking corn
Levant 0 1 0 3% No spray recommended
Lewiston 0 0 0 0% No spray recommended
Livermore Falls 0 0 0 3% No spray recommended
Monmouth 0 0 No spray recommended
New Gloucester 7 3 0 5-day spray interval recommended on all silking corn
Nobleboro 2 0 1 5% 6-day spray interval recommended on all silking corn
No. Berwick 1 0 0 2% No spray recommended
Oxford 0 1 0 24% One spray recommended for ECB feeding
Palmyra 0 0 0 2% No spray recommended
Poland Spring 0 0 0 7% No spray recommended
Sabattus 0 0 0 18% One spray recommended for ECB+FAW feeding
Wales 0 0 0 5% No spray recommended
Warren 0 0 0 2% No spray recommended
Wells I 1 0 0 2% No spray recommended
Wells II 0 0 0 1% 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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