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Sweet Corn IPM Newsletter No. 11 – September 6, 2013

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Sweet Corn

Sweet Corn IPM Newsletter No. 11 – September 6, 2013

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

Last Regular Issue for 2013

LATE SILKING CORN STILL NEEDS PROTECTION

Higher Earworm Counts in Southern and Coastal Locations

This will be the final issue of the Sweet Corn IPM Newsletter for the 2013 season. I would like to thank all of the growers who participated in the program this year, and our team of IPM scouts including Kara Rowley, Hayden Koller, Tammy Cushman, Griffin Dill and Sean McAuley, with help from John Hutton. Thanks to Pam St. Peter for getting us to print and keeping up the web page.  Input from our readers is welcome. Please call or e-mail us with your questions, comments and suggestions.

SITUATION
The storm last week appears to have brought some corn earworm moths into the state, as well as several inches of rain. Post Labor Day corn has matured quickly, but the market seems to be holding well, even with a plentiful supply. Insect pressure is relatively low for this late in the summer, especially in more northern and inland sites; although any weather coming up from the tropics over the next few weeks could change that status very quickly.

European corn borer:  Moth catches were fairly low and sporadic this week. A weak second generation appears to be showing up in a few locations, but most sites are well under threshold. Fields in Dayton, North Berwick, Wayne and Wells exceeded the threshold of 5 moths per week in silking corn, but only the Wayne field is not presently under a spray interval for corn earworm.

Corn earworm:  Moth counts were higher in some southern and coastal locations this week, suggesting that the recent storm may have brought in some moths. A 4-day spray interval for fresh silking corn was recommended at one site in Cape Elizabeth. A 5-day spray interval was recommended in Monmouth and the other Cape Elizabeth site. A 6-day spray interval was recommended for silking fields in Biddeford, a Dayton site, New Gloucester, North Berwick, Poland Spring, Sabattus, Warren and one Wells site. Remember that any storm fronts moving up from the south can bring lots of corn earworm with them and change the situation rapidly for any silking corn remaining.

Corn Earworm Larvae

Corn Earworm Larvae, photo by David Handley

Fall Armyworm Injury on Corn Leaves

Fall Armyworm Injury on Corn Leaves, photo by David Handley

Fall armyworm:  Moth counts were higher in some sites this week, but most remain under threshold for silking corn. Fall armyworm exceeded the threshold of three moths for silking corn in Cape Elizabeth, Dayton, Monmouth, New Gloucester, Nobleboro, Oxford, Warren and Wells.

Remember to plow down your corn stalks.
Plowing down corn stalks destroys overwintering sites for European corn borer. Winter rye can be planted after plow down to prevent soil erosion and conserve nutrients.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted Wing Drosophila Alert:  Fruit fly counts are increasing significantly this week and we’re getting more reports of larvae in ripening fruit, including fall raspberries, blueberries, blackberries and grapes. All ripening fruit should be protected with regular and repeated treatments of an approved insecticide. In most fields a 4 to 5 day spray interval is needed to prevent infestation.  Visit our website for details:  http://umaine.edu/highmoor/spotted-wing-drosophila/.

The New England Vegetable & Fruit Conference will be held in Manchester, New Hampshire on December 17, 18, and 19, 2013. Program and registration information will be coming soon.  Visit the website: http://www.newenglandvfc.org/.

Sincerely,

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
Moths
ECB
Moths
FAW
Moths
Recommendations / Comments
Auburn 0 0 0 No spray recommended
Biddeford 3 2 1 6-day spray interval recommended on all silking corn
Cape Elizabeth I 4 3 0 5-day spray interval recommended on all silking corn
Cape Elizabeth II 12 0 5 4-day spray interval recommended on all silking corn
Dayton I 1 3 3 One spray recommended for FAW on all silking corn
Dayton II 3 11 1 6-day spray interval recommended on all silking corn
Farmington 0 1 1 No spray recommended
Lewiston 0 3 0 No spray recommended
Monmouth 4 3 3 5-day spray interval recommended on all silking corn
New Gloucester 2 0 3 6-day spray interval recommended on all silking corn
Nobleboro 0 0 6 One spray recommended for FAW on all silking corn
No. Berwick 3 8 0 6-day spray interval recommended on all silking corn
Oxford 0 0 3 One spray recommended for FAW on all silking corn
Poland Spring 2 0 0 6-day spray interval recommended on all silking corn
Sabattus 2 1 1 6-day spray interval recommended on all silking corn
Wales 0 0 2 No spray recommended
Warren 3 2 9 6-day spray interval recommended on all silking corn
Wayne 0 6 0 One spray recommended for ECB on all silking corn
Wells I 0 0 0 No spray recommended
Wells II 2 5 5 6-day spray interval recommended on all silking corn

 

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:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

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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