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Sweet Corn Pheromone Trap Network for Western New York,
This is a seasonal scouting report giving growers in the Western New York area information on the presence of sweet corn pests and recommendations on scouting and thresholds. The report is written by Abby Seaman, NYS IPM's Area Extension Educator for Vegetables.
ECB-E catches are a mixed bag this week, increasing at some locations and decreasing at others. ECB-Z catches are generally up from last week. Small newly hatched larvae are being found in fields this week, but at relatively low numbers. The earliest fields are starting to show tassel. Still a few CEW moths flying at some locations.
Watch for common armyworm migrating from small grain fields into corn and other vegetable crops. I've heard about them marching across roads in large numbers, and infesting peppers, strawberries, and lawns in addition to corn. If they are a problem in sweet corn, the 15% infested plants threshold applies for pre-tassel corn, and 5% for silking corn. Scout fields even if they are not at the tassel emergence stage, especially if small grain or grass cover crop or hay fields are nearby.
Corn should be first scouted for ECB at early tassel emergence. Even at a location with high ECB populations, insecticide applications to whorl stage corn did not result in improved control when compared with one or two well-timed applications at tassel emergence. 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 whorl 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 they will be again protected from sprays. In fields with uneven development, two applications may be necessary, one when approximately 25-50% if the tassels have emerged, and again after 75% of the tassels have emerged, if the field is still over threshold.
The threshold for ECB at tassel emergence is 15% infested plants. Look down into emerging tassels for tiny larvae or frass (white to brown material about the size of fine sand). Before any insecticides have been applied, scouting is fast and easy because any sign of feeding is an almost sure sign of live larvae, so it's not necessary to spend time finding the larvae. After the initial insecticide application, feeding damage may be from a larva that has already been killed, so finding the critter is more important for an accurate count.
The numbers below are the weekly total for each location.