Sweet Corn IPM Newsletter No. 3 – July 10, 2014
Click on photos to enlarge.
FALL ARMYWORM, CORN EARWORM THREATEN SILKING CORN
Late Blight Alert for Potatoes and Tomatoes!
Last weekend’s storm will likely increase insect activity by bringing up moths from the south. Fortunately, the winds were not strong enough to cause widespread lodging in cornfields. More fields are coming into silk as the warm temperatures continue to push growth. More silking fields are now on a spray regime for corn earworm and/or fall armyworm. The first indication of late blight in Maine was found this week in a potato field in Buxton.
European corn borer: Moth catches were higher in some locations this week but continue to be erratic. Silking fields in Cape Elizabeth and Sabattus were over the threshold of 5 moths per week in traps, and a spray for silking corn was recommended. European corn borer feeding damage was over threshold in pre-tassel to tasseling fields in Biddeford, Bowdoinham, Lewiston and Sabattus this week. Remember that sprays applied at pre-tassel tend to be more effective than whorl or tassel stage sprays, because the larvae are usually more exposed.
Corn earworm: The impact of the tropical storm does not yet seem to be showing up in moth counts. Moths were higher in one Cape Elizabeth location and more sights are now catching their first moths, including our more northern sites, but there has not yet been a large bump in trap captures. A 6-day spray interval was recommended for early silking fields in Dayton, New Gloucester and one Lewiston site. A 4-day spray interval was recommended for one silking field in Cape Elizabeth.
Fall armyworm: Moth counts were up significantly in some locations while others still have yet to catch their first fall armyworm. Fields in Cape Elizabeth, New Gloucester and Lewiston were over the threshold of 3 moths per week in silking corn. However, these fields were also on a spray regime for corn earworm, so no additional sprays should be needed. The first feeding damage on plants from fall armyworm was noted this week in fields in Biddeford and Lewiston. Although not yet threatening alone, when combined with European corn borer damage the total feeding exceeded the 15% threshold.
Squash vine borer moths were caught in pheromone traps in North Berwick, Biddeford, Dayton and New Gloucester this week. The threshold of five moths per week was exceeded in North Berwick, Wells, Dayton and Biddeford. This pest threatens summer squash, winter squash and pumpkins. Unlike many moths, squash vine borer moths fly during the day. They are black and orange and resemble wasps. The moths lay eggs at the base of squash plants. The larvae bore into the base of the plants, causing vines to wilt and eventually collapse. See the 2014-2015 New England Vegetable Management Guide for control options.
Late Blight Alert! The first symptoms of late blight were found in a potato field in Buxton this week. This devastating disease of tomatoes and potatoes spreads via spores under warm, wet conditions. Growers should take precautions by applying preventative fungicides. See our publications website and the 2014-2015 New England Vegetable Management Guide for management options.
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
Sweet Corn IPM Weekly Scouting Summary
|%FeedingDamage||Recommendations / Comments|
|Biddeford||1||3||2||40%||One spray recommended for ECB + FAW|
|Bowdoinham||0||3||0||22%||One spray recommended for ECB|
|Cape Elizabeth I||0||5||0||5%||One spray recommended for ECB on silking corn|
|Cape Elizabeth II||8||3||12||1%||4-day spray interval recommended on all silking corn|
|Charleston||0||0||0||0%||No spray recommended|
|Dayton I||2||0||0||6-day spray interval recommended on all silking corn|
|Dayton II||2||0||0||9%||6-day spray interval recommended on all silking corn|
|Farmington||1||1||1||12%||No spray recommended|
|Garland||1||6||1||0%||No spray recommended (no silking corn)|
|Levant||0||4||1||0%||No spray recommended (no silking corn)|
|Lewiston I||1||1||0||0%||No spray recommended|
|Lewiston II||2||0||3||20%||6-day spray interval recommended on all silking corn|
|Livermore Falls||1||0||0||3%||No spray recommended|
|New Gloucester||2||4||6||1%||6-day spray interval recommended on all silking corn|
|No. Berwick||0||0||1||10%||No spray recommended|
|Oxford||0||1||0||5%||No spray recommended|
|Palmyra||0||15||0||1%||No spray recommended (no silking corn)|
|Sabattus||0||29||0||34%||One spray recommended for ECB on silking corn|
|Wales||0||2||0||3%||No spray recommended|
|Warren||0||0||0||13%||No spray recommended|
|Wells I||1||0||0||5%||No spray recommended|
|Wells II||0||0||1||0%||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.
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.