Nineteen of 37 sites reported this week. European corn borer (ECB)-E was caught at seven sites and ECB-Z was caught at four sites. Corn earworm was caught at four sites with Eden high enough to be on a six day spray interval (see table below).  No fall armyworm (FAW) or Western bean cutworm (WBC) were caught this week.

Most sites are at or reaching peak flight for ECB (630 DD modified base 50) and ECB damage and larvae were seen this week in whorl stage corn. When scouting focus on the emerging tassel. Separate the leaves and look down into the tassel for any signs of feeding, frass or larvae (see photos). The threshold for ECB is 15% infested plants at tassel emergence.

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 again they will be protected from sprays (see photos below for tassel stages). In fields with very uneven development, two applications may be necessary, one when approximately 25-50% of the tassels have emerged, and again after 75-100% of the tassels have emerged, if the field is still over threshold.

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