Sweet Corn IPM Newsletter No. 11 – September 6, 2018
Sweet Corn IPM Newsletter No. 11 – September 6, 2018
Click on photos to enlarge.
Last Issue for 2018!
MAJOR CORN EARWORM FLIGHT THREATENS LATE CORN
Any Late Silking Fields Remaining Require Tight Spray Interval
This will be the final issue of the Sweet Corn IPM Newsletter for the 2018 season. I would like to thank all of the growers who participated in the program this year, and our team of IPM scouts, including Lindsey Ridlon, Althea Hicks, Megan Knowles and Sean McAuley. Have questions, comments or suggestions about the program? Please call or email us.
SITUATION
Many farms will be finishing up corn harvest this week or next, as more hot, humid weather has hastened corn maturity and shortened the harvest season. Recent weather fronts from the west and south have brought a major flight of corn earworm and, to a lesser extent, fall armyworm into the state, most notably in southern and coastal sites. As a result, any late silking corn remaining will need to be protected regularly and often until the silks are completely dry.
European corn borer: Although we started removing borer traps from fields last week, farms with traps remaining showed very little activity. Single moths were caught in traps in North Berwick, Wells and Sabattus. No sites were over the 15% spray threshold for larval feeding damage. Here’s another reminder to plow down your corn stalks after harvest. Plowing down the stalks destroys overwintering sites for European corn borer.
Corn earworm: This week saw a significant jump in the number of moths found in our traps, indicating a severe threat to any silking corn remaining. Southern and coastal sites are being hardest hit, with some traps capturing over 100 moths. A 6-day spray interval for silking corn was recommended for Lewiston and Palmyra. A 5-day spray interval was recommended for Levant. A 4-day spray interval was recommended for silking fields in Charleston, Corinth, Dayton, Monmouth, New Gloucester, Nobleboro, Oxford, Poland Spring, Sabattus, Wayne and Wells. A 3-day spray interval was recommended for North Berwick, Biddeford and Cape Elizabeth.
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- Corn Earworm Feeding on Corn; photo by David Handley
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- Fall Armyworm Eggs on Corn; photo by David Handley
Fall armyworm: Armyworm moth numbers were higher at nearly all locations this week, similar to corn earworm. Fields in Biddeford, Cape Elizabeth, Dayton, Levant, Lewiston, Monmouth, New Gloucester, Nobleboro, North Berwick, Oxford, Poland Spring, Wayne, and Wells were all over the three moths per week spray threshold for silking corn.
Sincerely,
David T. Handley
Vegetable and Small Fruit Specialist
Highmoor Farm, P.O. Box 179, 52 US Route 202, Monmouth, ME 04259, 207.933.2100
UMaine Extension Diagnostic Research Lab, Pest Management Unit, 17 Godfrey Drive, Orono, ME 04473, 1.800.287.0279
| Location | CEW Moths | ECB Moths | FAW Moths | Recommendations / Comments |
|---|---|---|---|---|
| Biddeford | 149 | 0 | 26 | 3-day spray interval recommended on all silking corn |
| Bowdoinham | 1 | 2 | No spray recommended | |
| Cape Elizabeth I | 113 | 0 | 23 | 3-day spray interval recommended on all silking corn |
| Cape Elizabeth II | 500+ | 121 | 3-day spray interval recommended on all silking corn | |
| Charleston | 15 | 0 | 0 | 4-day spray interval recommended on all silking corn |
| Corinth | 13 | 0 | 0 | 4-day spray interval recommended on all silking corn |
| Dayton | 73 | 0 | 19 | 4-day spray interval recommended on all silking corn |
| Levant | 5 | 0 | 4 | 5-day spray interval recommended on all silking corn |
| Lewiston | 2 | 0 | 8 | 6-day spray interval recommended on all silking corn |
| Monmouth | 15 | 10 | 4-day spray interval recommended on all silking corn | |
| New Gloucester | 75 | 41 | 4-day spray interval recommended on all silking corn | |
| Nobleboro | 11 | 4 | 4-day spray interval recommended on all silking corn | |
| North Berwick | 112 | 1 | 3-day spray interval recommended on all silking corn | |
| Oxford | 8 | 96 | 4-day spray interval recommended on all silking corn | |
| Palmyra | 2 | 1 | 0 | 6-day spray interval recommended on all silking corn |
| Poland Spring | 71 | 6 | 4-day spray interval recommended on all silking corn | |
| Sabattus | 11 | 1 | 1 | 4-day spray interval recommended on all silking corn |
| Wayne | 36 | 13 | 4-day spray interval recommended on all silking corn | |
| Wells I | 11 | 0 | 1 | 4-day spray interval recommended on all silking corn |
| Wells II | 64 | 0 | 38 | 4-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
| 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:
UMaine Cooperative Extension Integrated Pest Management
UMass Amherst Integrated Pest Management
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.
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