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Corn Earworm Alert for Southern Minnesota Sweet Corn

Corn Earworm (CEW) moth flights have been relatively low this year up until this week. Although the flights remain low at most locations, during the past week CEW numbers increased at Blue Earth to over 160 per trap per night. 

As noted in previous articles, CEW is not able to overwinter successfully in MN, but migrates north this time of year from southern states. We’ve had some major southerly storms pass through the state, including Aug 7-8th that likely assisted with the recent influx of moths.


Corn earworm larvae in sweet corn (E. Burkness, UMN)

Although we have observed various levels of CEW resistance to pyrethroid insecticides (bifenthrin, lambda-cyhalothrin) in recent years, our results last year indicated good efficacy but we had low-moderate pest pressure. If you are not finding good/excellent control, consider one of the diamide options (e.g., Coragen) or methomyl. 

Unfortunately, the organic-certified Entrust and Pyganic only perform well in low-pressure situations. The good news is that our first two sweet corn planting dates at Rosemount, had 100% clean ears. However, this time of year is typically when CEW moth flights take off at most locations, and most of the mid- to late-planted sweet corn will continue to be attractive for CEW egg-lay. Growers should continue to watch the VegEdge moth flight page for CEW. European corn borer (ECB) moth flights can be monitored here as well. 

CEW egg-lay can continue throughout the next 4-5 weeks, as long as we maintain warm nights (>50F) and reasonable heat, or degree days through September.

For more information, see the detailed CEW-ECB article here.  

Authors: Bill Hutchison, Extension Entomologist, & Eric Burkness, Dept. of Entomology, University of Minnesota

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