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Sweet Corn IPM Newsletter No. 14 – September 17, 2012

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Sweet Corn

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

Last Issue for 2012

ANY FRESH SILKING CORN REMAINING NEEDS PROTECTION

Corn Earworm Still a Threat to Late Corn

This will be the final issue of the Sweet Corn IPM Newsletter for the 2012 season.  I would like to thank all of the growers who participated in the program this year, and our team of IPM scouts including John Banville, Tammy Cushman, Chase Gaewski, Griffin Dill and Sean McAuley, with help from John Hutton and Kara Rowley.  Special thanks go to Katie Woodman who coordinated the team.

SITUATION
Hurricane Isaac appears to have only caused a mild bump in pest numbers over the past week, and it is likely that cooler temperatures will slow pest activity in the coming days.  Any silking corn remaining requires protection from corn earworm statewide, but fall armyworm and European corn borer are only at problem levels in a few sites.

European corn borer:  Moth counts continued to be very low last week in most locations.  Although fields in Oxford and Wayne exceeded the 5-moth threshold for silking corn, which suggests the start of a second generation.  Both sites are on spray schedules for corn earworm, so no additional sprays were needed.  Feeding damage was found in a pre-silking field in Biddeford, and exceeded the 15% threshold when combined with fall armyworm damage.

European Corn Borer Larva on Ear

European Corn Borer Larva on Ear, photo by David Handley

Corn earworm:  Moth counts were generally higher last week, returning many fields to tighter spray intervals on fresh silking corn.  A 4-day spray interval for silking corn was recommended for Cape Elizabeth, Dayton, Levant, New Gloucester, Nobleboro, North Berwick, Wales,Wayne and Warren.  A 5-day spray interval was recommended for Biddeford, Dresden, Lewiston, and one Wells location.  A 6-day spray interval was recommended for Jefferson, Oxford, Poland Spring and Wells.

Corn Earworm

Corn Earworm, photo by David Handley

Fall armyworm:  Most fields are under spray schedules for corn earworm, so little feeding damage is being noted.  Only one Biddeford field was over the threshold when combined with ECB feeding damage.  Moth captures remained low, with only one field in Levant exceeding the spray threshold of 3 moths in silking corn.  Single moths were caught in Lewiston, Monmouth and New Gloucester.

Adult Fall Armyworm

Adult Fall Armyworm, photo by David Handley

It’s time for cover crops!
Plowing down corn stalks destroys the over wintering sites of European corn borer, but late plowing can leave soil prone to erosion during the winter and spring.  Planting winter rye is a good option for many fields.  It can be planted well into September to produce enough of a cover to prevent erosion. Rye will survive the winter and put on more growth in the spring.  It should be killed by plowing, mowing or herbicide before it goes to seed.  Having rye on the field may delay planting in the spring, as you must wait for conditions to be warm and dry enough to plow it in.  Animal manures can also be applied to soils in early fall and incorporated to improve soil structure and provide nutrients.  Cover crops should be seeded after manure applications to absorb and hold nutrients, which will be released after the crop is plowed down the following spring.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                      Pest Management Office
P.O. Box179                          491 College Ave
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
%Feeding
Damage
Recommendations / Comments
Biddeford 5 0 0 24% 5-day spray interval for all silking corn
Cape Elizabeth I 9 0 0 All Silk 4-day spray interval for all silking corn
Cape Elizabeth II 18 0 0 All Silk 4-day spray interval for all silking corn
Dayton I 8 0 0 All Silk 4-day spray interval for all silking corn
Dresden 4 0 0 All Silk 5-day spray interval for all silking corn
Jefferson 2 0 0 All Silk 6-day spray interval for all silking corn
Levant 15 0 3 All Silk 4-day spray interval for all silking corn
Lewiston 6 0 1 All Silk 5-day spray interval for all silking corn
Monmouth 0 0 1 All Silk No spray recommended
New Gloucester 38 0 1 All Silk 4-day spray interval for all silking corn
Nobleboro 33 0 0 All Silk 4-day spray interval for all silking corn
North Berwick 17 0 0 All Silk 4-day spray interval for all silking corn
Oxford 3 13 0 All Silk 6-day spray interval for all silking corn
Poland Spring 2 1 0 All Silk 6-day spray interval for all silking corn
Wales 23 1 0 All Silk 4-day spray interval for all silking corn
Wayne 11 10 0 All Silk 4-day spray interval for all silking corn
Warren 9 0 0 All Silk 4-day spray interval for all silking corn
Wells I 3 0 0 All Silk 6-day spray interval for all silking corn
Wells II 5 0 0 All Silk 5-day spray interval for 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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