Twenty-one sites reporting this week. Sixteen sites reporting European corn borer (ECB)-E. Seneca Castle had the high count again this week with 225 moths caught. ECB-Z was reported from eight sites. Corn earworm (CEW) was caught at twelve sites with eight sites high enough to require a 6, 5, or 4 day spray interval (see spray table at bottom of post). Nine sites reporting Fall armyworm (FAW) and twenty sites reporting Western bean cutworm (WBC).

Several sites reporting feeding damage by FAW in whorl stage corn. The larvae feeding in the whorl are protected from insecticide applications and mortality will not be as high as at tassel emergence, when larvae feeding in the emerging tassel are exposed to the spray.  Larvae will leave the tassel as it opens up and no longer provides a moist, protected feeding environment, and move down the plant looking for protected places to feed.  Insecticide applications need to be timed to kill larvae before they bore into a new feeding location where they will be again protected from sprays.  In fields with very uneven development, two applications may be necessary, one when approximately 25-50% if the tassels have emerged, and again after 75-100% of the tassels have emerged, if the field is still over threshold. The threshold for ECB and FAW at tassel emergence is 15% infested plants. To learn how to scout sweet corn please see the video titled: How to Scout Fresh Market Sweet Corn.

J.W. Apple, Department of Entomology, University of Wisconsin-Madison

Percent WBC moth emergence, data from University of Nebraska