Thirty-two sites reporting this week. European corn borer (ECB)-E was trapped at twelve sites and ECB-Z was trapped at five sites. Corn earworm (CEW) was trapped at eleven sites, with five sites high enough to be on a 5 or 6 day spray schedule (see chart below). Fall armyworm (FAW) was trapped at seven sites and Western Bean cutworm (WBC) was trapped at nineteen sites this week.

Western bean cutworm numbers are beginning to increase. Peak flight usually occurs around the first week of August. It is important to begin scouting for egg masses even if cumulative trap catches have not reached 100, as egg masses have been found when cumulative trap catched were still in the single digits. WBC will usually lay eggs on the upper side of the top 1-3 leaves of pre-tassel corn, close to the leaf base. After tasseling has finished WBC seek out younger corn or dry beans. To scout for egg masses check the top 3 leaves of ten corn plants in ten locations throughout the field. The eggs are easy to observe if you view the leaf while holding it towards the sun. The egg mass will appear as a distinct shadow (see photo).

It takes between 5-7 days for eggs to hatch. It is critical that sprays are timed before the larvae have a chance to enter the ear. The egg mass will become purple in color approximately 24 hours before egg hatch (see photo).

Percent WBC moth emergence, data from
University of Nebraska