Sweet Corn IPM Newsletter No. 12 – September 1, 2010
September 2nd, 2010 
For full page print version, please see link at the bottom.
Corn Earworm & Fall Armyworm Pressure Slightly Higher
Predicted Tropical Storms May Further Increase Moth Pressure
SITUATION
Warm, dry weather continues to mature late-planted corn rapidly and keep moths flying into our fields. Moth counts were somewhat higher this week, as we would expect with this stretch of weather; but these insects are finding much less fresh silking corn around as the harvest season speeds to an end. Two hurricanes/tropical storms are heading our way over the next week or so which could threaten remaining corn fields with flooding, lodging from high winds, and lots of corn earworm and armyworm moths brought up on the storms from the south.
European corn borer: Moth counts continue to be very low and very little larval feeding has been evident this week. No fields were over threshold for European corn borer moths in silking cornfields, and no significant feeding injury in younger corn was found at any of the sites.
Corn earworm: Pheromone trap catches were a bit lower in most locations this week, but remain high enough to require fairly short spray intervals at many sites. Four-day spray intervals were recommended in Cape Elizabeth, Corinth, Dresden, Jefferson, Levant, Lewiston, Monmouth, Nobleboro, North Berwick, Old Town, Oxford, Poland Spring, Readfield, Warren and one site in Wells. Five-day spray intervals were recommended in Biddeford, Dayton, Wales and a site in Wells. A six-day spray interval was recommended in Wayne.
Corn Earworm Feeding on Corn, photo by David Handley
Fall armyworm: Moth counts were higher in some locations this week, but still quite variable from site to site. Moths exceeded threshold of three per week in silking corn in Biddeford, Cape Elizabeth, Corinth, Dayton, Jefferson, Lewiston, Monmouth, Nobleboro, North Berwick, Old Town, Poland Spring, Readfield, Warren and one site in Wells. All of these fields were already on a spray interval for corn earworm, so no additional sprays were recommended. Fall armyworm feeding injury exceeded the 15% threshold for pre-silking corn in Nobleboro and one site in Wells.
It’s time for cover crops!
Plowing down corn stalks destroys the overwintering 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. Using no-till, strip-till or zone-till techniques can allow earlier seeding because you don’t need to plow, but these require specialized equipment. Soils tend to stay cooler in the spring when using these techniques, so be sure that temperatures are warm enough to allow seed germination before you plant. Animal manures can also be applied to soils in the late summer and early fall and incorporated into the soil to improve soil structure and provide nutrients. Cover crops should be seeded following the manure application to absorb and hold onto soil nutrients, which will be released after the crop is plowed down the following spring.
Corn Harvester, photo by David Handley
Unplowed Corn Field, photo by David Handley
Sincerely,
David T. Handley
Vegetable & Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box 179 491 College Ave
Monmouth, ME 04259 Orono, ME 04473
(207) 933-2100 1-800-287-0279
Sweet Corn IPM Weekly Scouting Summary
| Location | CEWMoths | ECBMoths | FAWMoths | %ECB +FAW | Recommendations / Comments |
| Biddeford | 5 | 0 | 11 | 2% | 5-day spray interval recommended for all silking corn |
| Cape Elizabeth I | 24 | 0 | 4-day spray interval recommended for all silking corn | ||
| Cape Elizabeth II | 11 | 0 | 27 | 4-day spray interval recommended for all silking corn | |
| Corinth | 17 | 0 | 9 | 4-day spray interval recommended for all silking corn | |
| Dayton II | 5 | 0 | 5 | 5-day spray interval recommended for all silking corn | |
| Dresden | 44 | 3 | 1 | 4-day spray interval recommended for all silking corn | |
| Jefferson | 8 | 0 | 13 | 4-day spray interval recommended for all silking corn | |
| Levant | 24 | 0 | 0 | 3% | 4-day spray interval recommended for all silking corn |
| Lewiston I | 11 | 0 | 8 | 4-day spray interval recommended for all silking corn | |
| Lewiston II | 63 | 0 | 9 | 4-day spray interval recommended for all silking corn | |
| Monmouth | 18 | 0 | 22 | 4-day spray interval recommended for all silking corn | |
| Nobleboro | 38 | 4 | 74 | 85% | 4-day spray interval recommended for all silking corn |
| North Berwick | 20 | 0 | 3 | 7% | 4-day spray interval recommended for all silking corn |
| Old Town | 17 | 0 | 4 | 4-day spray interval recommended for all silking corn | |
| Oxford | 12 | 0 | 0 | 4-day spray interval recommended for all silking corn | |
| Poland Spring | 39 | 0 | 3 | 4-day spray interval recommended for all silking corn | |
| Readfield | 24 | 1 | 3 | 4-day spray interval recommended for all silking corn | |
| Wales | 5 | 0 | 0 | 5-day spray interval recommended for all silking corn | |
| Warren | 11 | 0 | 14 | 4-day spray interval recommended for all silking corn | |
| Wayne | 2 | 0 | 0 | 6-day spray interval recommended for all silking corn | |
| Wells I | 6 | 0 | 7 | 37% | 5-day spray interval recommended for all silking corn |
| Wells II | 17 | 0 | 0 | 4-day spray interval recommended 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.
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.
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.
Tags: corn, Highmoor Farm, pest management, sweet corn
Posted in News
