Twenty-nine sites reporting this week. European corn borer (ECB)-E was trapped at seven sites and ECB-Z was trapped at six sites. Corn earworm (CEW) was trapped at nine sites, with four sites high enough to be on a 5 or 6 day spray schedule (see chart below). Fall armyworm (FAW) was trapped at three sites and Western Bean cutworm (WBC) was trapped at thirteen sites this week.

I scouted three fields this week that had ECB damage, over threshold, in the tassel. At two of the fields that tassels were broken over and the larvae had already entered the stalk. At the third site the tassels were just beginning to emerge from the whorl and the larvae were still actively feeding in the tassel. It is important to time spray applications to target the larvae when they leave the tassel but before they bore into the plant.

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.  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.

Percent WBC moth emergence, data from
University of Nebraska