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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.
European corn borer trap catches are up sharply this week and catches are very high at some locations. All locations are catching some moths. ECB egg masses are being found in some fields, and CEW moths are being caught at one location.
Fields started under plastic or row cover will be most attractive to egg-laying moths because the plants are larger than in bare ground fields. We have found using the usual tassel emergence scouting and thresholds for plastic or row cover corn doesn't work well. John Mishanec has had good results in trials in which pheromone trap catches were used to time sprays in row cover or plastic corn. Growers waited until there was a significant increase in the ECB trap catches in their area and then timed sprays to coincide with egg hatch. ECB eggs require 100 degree days (base 50) from oviposition to hatch. Under the weather conditions predicted for this week, eggs will take 6-7 days to hatch. A second spray may be needed 6-7 days later if trap catches remain high for a couple of weeks.
Bare ground fields should be first scouted for ECB larvae at early tassel emergence. Even at a location with high ECB populations, insecticide applications in bare ground fields 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 tassel 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 75-100% of the tassels have emerged, if the field is still over threshold.
The threshold for ECB and armyworms at tassel emergence is 15% infested
plants. For corn borers, look down into emerging tassels for tiny
larvae or frass (white to brown material about the size of fine sand).
For armyworms look for ragged feeding holes and frass pellets the texture
of coarse sawdust.