Sweet Corn IPM Newsletter No. 3 – July 12, 2013
For full page print version, please see link at the bottom. Click on photos to enlarge.
Yet more rain in southern Maine this week has kept fields wet and slowed growth, but more early planted fields are now coming into silk and first harvest is within sight. Insect activity has increased in most locations, and any silking corn is now threatened by both European corn borer and corn earworm.
European corn borer: Moth catches continue to be somewhat erratic this week, but most sites had relatively low counts. Silking fields in Gray, North Berwick and Sabattus were over the threshold of 5 moths per week in traps, but all of these 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 Biddeford, Cape Elizabeth, and Warren this week. We expect to see more late fields exceeding feeding injury in later plantings in the coming week. 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: Moths are now being caught at most locations, but many fields do not yet have silking corn and so are not yet threatened by corn earworm. A 6-day spray interval was recommended for early silking fields in Dayton, Gray, No. Berwick, Oxford, Sabattus and Wells. A 5-day spray interval was recommended for silking fields in Farmington, Garland, and Nobleboro, where moth counts were slightly higher. A 4-day spray interval was recommended for one silking field in Cape Elizabeth where the highest moth count of the season was found this week.
Fall armyworm: Single moths were caught in two locations this week (Farmington, Lewiston). At this time fall armyworm is not a threat to silking corn. We have not found any fall armyworm feeding damage in younger corn fields, but we anticipate that it will be showing up soon.
Squash vine borer moths were caught in pheromone traps in North Berwick, Biddeford, Gray, New Gloucester and Nobleboro. The threshold of five moths per week was only exceeded in North Berwick, but growers should be aware that the pest is now active and threatens summer squash, winter squash and pumpkins. See the New England Vegetable Management Guide for control options.
Late Blight: Grower and Farm Stand Alert
Late blight has been found on potato plants in northern Maine this week. This follows recent reports of late blight in tomato and potato plantings in New York and Massachusetts and many southern coastal states. Growers should be alert to catch early symptoms and be ready to apply appropriate control measures. Typical symptoms will be water-soaked lesions on the leaves with fine, white cottony mycelium on the undersides. Infections on the stems appear as dark, almost black lesions. Visit Cornell University Cooperative Extension’s web pages for photos of tomatoes and potatoes. Please report any suspicious symptoms to the Pest Management Office 581.3883 (1.800.287.0279), or email PMO@umext.maine.edu.
Reminder: Highmoor Farm Field Day and Summer Tour will be held on Wednesday, July 31, 2013 from 9:00 a.m. to 4:00 p.m. Registration fee is $20 per person, including lunch, and preregistration is strongly encouraged. For more information, visit the Highmoor Farm website or call 207.933.2100. 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
Sweet Corn IPM Weekly Scouting Summary
|Recommendations / Comments|
|Auburn||5||2||0||10%||No spray recommended (no silking corn)|
|Biddeford||1||1||0||63%||One spray recommended for ECB|
|Cape Elizabeth I||1||2||0||3%||No spray recommended|
|Cape Elizabeth II||43||2||0||77%||4-day spray interval recommended on all silking corn|
|Charleston||14||8||0||7%||No spray recommended (no silking corn)|
|Dayton||3||1||0||1%||6-day spray interval recommended on all silking corn|
|Farmington||4||1||1||5-day spray interval recommended on all silking corn|
|Dayton||0||0||0||0||No spray recommended|
|Garland||7||0||0||3%||5-day spray interval recommended on all silking corn|
|Gray||3||23||0||6-day spray interval recommended on all silking corn|
|Levant||4||2||0||0%||No spray recommended (no silking corn)|
|Lewiston||0||0||1||2%||No spray recommended|
|Livermore Falls||1||1||0||4%||No spray recommended|
|New Gloucester||1||2||0||2%||No spray recommended|
|Nobleboro||6||2||0||5-day spray interval recommended on all silking corn|
|No. Berwick||3||13||0||6-day spray interval recommended on all silking corn|
|Oxford||3||3||0||6-day spray interval recommended on all silking corn|
|Palmyra||0||8||0||2%||No spray recommended|
|Sabattus||2||12||0||6-day spray interval recommended on all silking corn|
|Wales||0||0||0||0%||No spray recommended|
|Warren||1||0||0||20%||One spray recommended for ECB|
|Wells I||2||0||0||0%||No spray recommended (no silking corn)|
|Wells II||3||4||0||4%||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.
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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Image Description: Sweet Corn
Image Description: European Corn Borer Trap
Image Description: European Corn Borer Larvae on Pre-tassel Stage Corn
Image Description: Corn Earworm Moth
Image Description: Late Blight on Tomato Leaf