Sweet Corn IPM Newsletter No. 12 – September 9, 2022

a pencil drawing of a corn plant ready to harvest.

Last Issue for 2022 Sweet Corn IPM Newsletter – No. 12 – September 9, 2022


Most Silking Fields Now Require Tight Spray Schedule

This will be the final issue of the Sweet Corn IPM Newsletter for the 2022 season. I would like to thank all of the growers who participated in the program this year, and our team of IPM scouts, including Brooke Martin, Karla Mendoza Yanes and Sean McAuley. Special thanks to Chris Howard for editing and mailing the newsletter and updating our webpage and blog.



Corn Harvester
Corn Harvester, photo by David Handley

Corn harvest is finishing up at many farms, as the intense heat during the summer hastened the maturity of later plantings. Late season pest pressure is largely from corn earworm, as numbers continued to climb at most sites this week.


European corn borer:  Larval feeding injury from corn borer was not over the 15% control threshold for pre-silking corn at any of our scouting sites. Moth captures are lower than last week and were not over the 5-moth threshold for silking corn at any location.


Corn earworm:  Moth counts increased at most southern locations this week.  A 6-day spray interval for silking corn was recommended for Monmouth and Wayne. A 5-day spray schedule was recommended for one site in Wells. A 4-day spray interval was recommended in Biddeford, Bowdoinham, Cape Elizabeth, Oxford, and one Wells site.  A 3-day spray interval was recommended at one Dayton site.


Male Fall Armyworm Moth
Male Fall Armyworm Moth; photo by David Handley

Fall armyworm:  Fall armyworm moth counts were variable around the state. Some sites saw increased numbers while other sites had no moths. Trap counts were over the three-moth threshold for silking corn in Biddeford, Bowdoinham, Cape Elizabeth, one Dayton site, one Lewiston site, New Gloucester, and Oxford.  Only the Lewiston site was not also on a spray schedule for corn earworm, so a single spray for all silking corn was recommended there.  Larval feeding damage on leaves and tassels of younger corn was not over threshold at any of the sites this week.


Spotted Wing Drosophila: There is now a very high threat level for any berry fields. Growers should maintain a tight, (5-7 day) spray schedule.



New England Vegetable & Fruit Conference: Hold the date! The Conference is back for a full three days of educational sessions and a large trades show.  Please plan to join us in Manchester, NH, December 13-15, 2022.


Annual end of corn season checklist:

  1. Plow down corn stalks and stubble to destroy overwintering larvae of European corn borer
  2. Plant a cover crop, such as winter rye, to prevent soil erosion and add organic matter to the soil.
  3. Take a soil test to determine if lime or other nutrients should be applied.
  4. Plan to rotate your crops to prevent pests from building up in any one location.
  5. Evaluate your weed management results; What worked well and what didn’t? Which weeds were the biggest problems?  How can you improve control?



David T. Handley

Vegetable and Small Fruit Specialist


Highmoor Farm                       UMaine Extension Diagnostic

P.O. Box 179                           Research Lab, Pest Mgmt. Unit

52 U.S. Route 202                   17 Godfrey Drive

Monmouth, ME  04259          Orono, ME  04473

207.933.2100                           1.800.287.0279



Sweet Corn IPM Weekly Scouting Summary


Location CEW








Recommendations / Comments
Biddeford 47 0 10 2% 4-day spray interval for silking corn
Bowdoinham 12 1 10 7% 4-day spray interval for silking corn
Cape Elizabeth 38 0 9 4-day spray interval for silking corn
Dayton I 99 0 3 3-day spray interval for silking corn
Dayton II 73 0 1 4-day spray interval for silking corn
Garland 0 0 0 No spray recommended
Lewiston 10 1 1 4-day spray interval for silking corn
Lewiston II 0 2 4 1 spray on all silking corn for FAW
Monmouth 4 0 2 6-day spray interval for silking corn
New Gloucester 51 0 3 4-day spray interval for silking corn
Oxford 8 3 5 4-day spray interval for silking corn
Palmyra 0 1 0 No spray recommended
Wayne 2 0 0 6-day spray interval for silking corn
Wells I 6 0 0 5-day spray interval for silking corn
Wells II 42 0 1 4-day spray interval for silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)

ECB: European corn borer

FAW: Fall armyworm


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.

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.


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