Twenty-eight sites reported this week with European corn borer (ECB)-E caught at three sites. ECB-Z was caught at seven sites. Nine sites reported corn earworm (CEW) with seven of those sites high enough to be on a 4, 5 or 6 day spray interval (see table at bottom of post). The first fall armyworm (FAW) moths were caught this week at 3 sites while no Western bean cutworm (WBC) have been caught yet this season. No hybrid ECB moths were caught at any of the 5 sites with traps.

Based on the accumulated degree days (base 86/50), most sites are in the first generation treatment period for the bivoltine ECB (see table below). Bivoltine means that the moth has two generations per season while univoltine moths have only one generation per season. We have both the bivoltine and univoltine ECB moths present in NY.

Below is the predicted percent emergence for the univoltine ECB based on a modified base 50F degree day model. Based on the model, we are just now beginning to enter the first emergence of the univoltine ECB and are still below 10% emergence for most of the sites.

Degree-day model for univoltine ECB from North Dakota.

Even though ECB trap catch numbers remain low, feeding damage has been observed in the field. If corn is in the tassel emergence stage, scout the tassel area for any signs of larvae or frass (Scouting and Threshold Information). The threshold for tassel emergence stage corn is 15%.  Eggs take approximately 100 base 50 degree days to hatch. Egg masses will change from white to cream to black as they age. When they appear black they are in the “black head” stage and will most likely hatch within 24 hours (see photos below). For growers using Trichogramma ostrinae, a beneficial wasp that will parasitize ECB eggs, releases should be made during the egg laying stage. For more information please refer to the fact sheet: Using Trichogramma ostriniae to help manage European corn borer in sweet corn, peppers, and potatoes.