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Sweet Corn IPM Newsletter No. 4 – July 19, 2013

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Sweet Corn IPM Newsletter No. 4 – July 19, 2013

Click on photos to enlarge.


Stalled Weather Pattern Means Little Change to Pest Situation

Most fields did not see significant rain this week; in fact some southern and northern fields are starting to run dry. The heat has pushed corn development rapidly and a couple of early fields are just ready for harvest. Some later plantings look a bit spotty, with uneven development due to the extended cool, wet weather following planting. Generally, insect activity has been light to moderate this week, with several fields not requiring any additional protection. A predicted change in the weather pattern next week may bring about some changes in pest activity as well.

European corn borer:  Moth catches have declined to very low numbers this week, with most farms having no moths in the traps. A silking field in Charleston was the exception with 19 moths, exceeding the threshold of 5 moths per week in traps, but all of this sites are also on a spray schedule for corn earworm, so no additional sprays should be required. European corn borer feeding damage was over threshold in pre-tassel fields in North Berwick and Warren this week.

European Corn Borer Larva

European Corn Borer Larva, photo by David Handley

Corn Earworm Moth

Corn Earworm Moth, photo by David Handley

Corn earworm:  Moth counts were generally low in southern Maine this week and many locations did not require protection. In the more northern sites, counts were higher, and more frequent sprays were needed on silking corn. A 4-day spray interval was recommended for Charleston and Garland. A 5-day spray interval was recommended for Levant. A 6-day spray interval was recommended for silking fields in Cape Elizabeth, Hollis and Farmington.

Fall Armyworm Moths

Fall Armyworm Moths (female right, male left), photo by James Dill

Fall armyworm:  A slight increase in fall armyworm moth activity was seen this week.  Single moths were caught in seven locations this week including Auburn, Biddeford, Farmington, Dayton, Nobleboro, Oxford and Wells. At one field in New Gloucester, five moths were caught, exceeding the three-moth threshold for the week, so a spray for all silking corn was recommended. We have found very little fall armyworm feeding damage in younger corn fields, but we expect that levels will be increasing soon.

Squash vine borer moths were caught in pheromone traps in North Berwick, Wells, Hollis, Biddeford, Gray, and New Gloucester this week. The threshold of five moths per week was exceeded in North Berwick, Hollis, Gray and New Gloucester. Be aware that this pest is now active and threatens summer squash, winter squash and pumpkins.  See the New England Vegetable Management Guide for control options.

Highmoor Farm Highmoor Farm Fruit and Vegetable Growers Field Day July 31, 2013
Please join us for the Highmoor Farm Field Day and Summer Tour to be held on Wednesday, July 31, starting at 9:00 a.m. Growers will have an opportunity to tour the fruit and vegetable research plots at the farm, part of the Maine Agricultural and Forest Experiment Station, and hear Extension specialists and guest speakers discuss current research on apples, grapes and vegetables. Maine State Legislators will also be on hand to offer updates on programs and legislation effecting farming in Maine.  Please join us for the program, farm tours and lunch.

Registration fee is $20 per person, including lunch and preregistration is strongly encouraged. Visit the Field Day website for more information. If you are a person with a disability and will need any accommodations to participate in this program, please call Pam St. Peter at Highmoor Farm, 207.933.2100 or TDD 1.800.287.8957 to discuss your needs at least 7 days prior to this event.


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 1 6% No spray recommended
Biddeford 1 0 1 14% No spray recommended
Cape Elizabeth I 1 0 0 7% No spray recommended
Cape Elizabeth II 2 0 0 6-day spray interval recommended on all silking corn
Charleston 9 19 0 2% 4-day spray interval recommended on all silking corn
Dayton 1 0 1 4% No spray recommended
Farmington 2 0 1 1% 6-day spray interval recommended on all silking corn
Garland 11 2 0 0% 4-day spray interval recommended on all silking corn
Gray 0 1 0 3% No spray recommended
Hollis 2 0 0 6-day spray interval recommended on all silking corn
Levant 5 0 0 1% 5-day spray interval recommended on all silking corn
Lewiston 0 0 0 0% No spray recommended
New Gloucester 0 0 5 One spray recommended on silking corn for FAW
Nobleboro 0 0 1 No spray recommended
No. Berwick 0 0 0 32% One spray recommended for ECB feeding
Oxford 0 0 1 4% No spray recommended
Palmyra 0 4 0 No spray recommended
Wales 0 1 0 6% No spray recommended
Warren 1 0 0 25% One spray recommended for ECB feeding
Wells I 0 0 0 2% No spray recommended
Wells II 0 1 1 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.

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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