Twenty-nine sites reporting this week. European corn borer (ECB)- E was caught a six sites and ECB-Z was caught at four sites. With a high count of 16 ECB-Z at the Penn Yan site. The hybrid ECB was only caught at the Seneca Castle site this week. Corn earworm was caught at tweleve sites with only five sites high enough to be on 4, 5 or 6 day spray schedule (see table below). The first fall armyworm (FAW) was caught this week at two sites (Bellona and Preble). Western bean cutworm numbers have really increased in just one week, with 17 sites reporting trap catches and one site already finding an egg mass.

WBC peak flight is expected late July into early 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).

To determine the estimated WBC flight completion of the sweet corn sites, use the degree days in the table below. Degree days were calculated using a base 38°F but not the upper threshold of 75°F. The degree days are therefore overestimated a bit. Most of our sites fall between 1-10% flight completion.

NEWA Western bean cutworm flight emergence lookup table.