European corn borer trap catches are generally up from last week at most locations.  Corn earworm catches are variable, ranging from 0 to a high of 12 this week.  Use the chart below and the trap catches from your area to determine the needed spray interval for green silk stage fields.  In areas where CEW is determining the spray schedule, any other larvae in the field will also be controlled.  Fall armyworm was caught in low numbers at a few locations.  Western bean cutworm catches are being caught at over half the trapping locations, with numbers in the high teens and low twenties at several locations.  This week may be the peak flight, some high trap catches are also being reported from a separate WBC trap network.  A threshold for WBC in sweet corn is still a question.  Information from Michigan and Ontario (note that the Ontario site refers to field corn not sweet corn) suggest a threshold of 5% infested plants is being used in field corn, 4%  infested plants in processing sweet corn and a 1% threshold in fresh market sweet corn.  In areas where CEW is not determining the spray schedule, scout late whorl – early tassel emergence fields for ECB and WBC egg masses and newly hatched larvae.  Not all areas have WBC catches high enough to expect to find them, so don’t be surprised if you don’t.  Scout the ear zone of silk stage fields for egg masses and newly hatched larvae.  See the links along the right side of the page for photos of all the sweet corn worm pests.

Recommended spray intervals based on CEW trap catches