Sweet Corn IPM Newsletter No. 4 – July 23, 2021

Sweet Corn
Corn IPM Newsletter Picture

Sweet Corn IPM Newsletter No. 4  – July 23, 2021

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Corn Earworm, Fall Armyworm & European Corn Borer Numbers Higher


Early corn harvest is underway in Southern Maine.  Recent rains have made access to some fields difficult as we experience a second mud season for the year.  Our traps caught all of the major corn pests this week, exceeding the spray threshold for silking corn in several locations. Western bean cutworm counts were also higher, adding another threat for the season.


European Corn Borer Larva
European Corn Borer Larva; photo by David Handley



European corn borer:

Larval feeding injury was not over the 15% control threshold in any locations this week although low levels of feeding activity was observed in most fields. European corn borer moth trap counts were over the spray threshold of 5/week in: Auburn, Monmouth, Sabattus, Wells, and one Dayton site. The Auburn and Sabattus sites are also under a spray schedule for corn earworm, which should provide control of corn borer.




Corn Earworm Moth
Corn Earworm Moth; photo by David Handley

Corn earworm:  

Moth captures in pheromone traps were spotty around the state this week, but there is an upward trend in their populations. Silking fields in one Well site are on a 6-day spray interval to protect against corn earworm. Auburn and Farmington sites are on a 5-day spray schedule, and New Gloucester has a 4 day spray schedule recommended.  Other sites had very low or no moth counts this week, but expect that situation to change soon, and continue to monitor silking corn.


Fall Armyworm Moths
Fall Armyworm Moths (female right, male left); photo by James Dill

Fall armyworm:

We caught fall armyworm moths in most locations this week.  Fall armyworm larvae threaten corn by feeding voraciously on foliage, tassels and chewing into the ears. Moths may also lay eggs on silking corn, allowing the larvae to move into the ears through the silk channels while leaving no visible feeding injury on the plants. Counts were over the threshold of 3 moths per week in silking corn in Cape Elizabeth, Garland, and New Gloucester.  The New Gloucester site is also on a spray schedule for corn earworm, which should provide protection against fall armyworm.  We have not yet found any feeding damage in the field, but expect it will become visible soon.


Western bean cutworm moth
Western Bean Cutworm moth; photo by Lindsey Ridlon



Western Bean Cutworm:

Moth counts were higher this week in most locations. This “new” pest behaves similarly to fall armyworm on sweet corn,  feeding on foliage and entering the ears. Sprays are recommended when feeding levels reach 8% in a field, or when moths are active in silking fields.



Three Squash Vine Borer Moths
Three Squash Vine Borer Moths; photo by Lindsey Ridlon



Squash vine borer:

We are catching moths in pheromone traps this week and damage is being reported in some southern fields. Be on the lookout for squash vine borer feeding at the base of the plants and/or wilting vines and apply appropriate control if damage is found.





cedar waxwing
Cedar Waxwing; photo by C. Eves-Thomas


Birds are already causing injury to corn ears in some fields. Repelling birds can be a big challenge for growers.  Recent research has found that scare eye balloons and air dancers can reduce injury significantly if placed correctly.  De-tasseling immediately following pollination was very effective in deterring birds, but is labor intensive.  You can find a summary of the research through this link



David T. Handley

Vegetable & Small Fruit Specialist


Highmoor Farm            Pest Management Unit

P.O. Box 179                 17 Godfrey Drive

52 U.S. Route 202        Orono, ME  04473

Monmouth, ME  04259

207.933.2100                1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW








Recommendations / Comments
Auburn 4 14 1 5% 5-day spray interval for silking corn
Biddeford 0 0 0 4% No spray recommended
Bowdoinham 0 1 0 3% No spray recommended
Cape Elizabeth 0 0 3 3% One spray for FAW on silking corn
Dayton I 0 3 0 0% No spray recommended
Dayton II 0 8 1 2% One spray for ECB on silking corn
Farmington 4 1 1 2% 5-day spray interval for silking corn
Garland 1 1 10 0% One spray for FAW on silking corn
Lewiston 0 0 0 0% No spray recommended
Monmouth 0 32 0 8% One spray for ECB on silking corn
New Gloucester 15 1 28 3% 4-day spray interval for silking corn
Oxford 0 0 0 2% No spray recommended
Palmyra 0 0 0 0% No spray recommended
Sabattus 1 16 2 7% One spray for ECB on silking corn
Wayne 0 1 0 5% No spray recommended
Wells I 0 5 0 0% One spray for ECB on silking corn
Wells II 2 3 2 0% 6-day spray interval for silking corn

*Traps just set up-no data yet

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.

IPM Web Pages:

UMaine Extension IPM

Pest Watch


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