|->Home > scouting > scnetwork > scnetwork04
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 catches are still increasing in many areas, but not at the rate we were seeing last week. I received two reports today that small ECB larvae are being found in the emerging tassel of the earliest planted fields.
Split field demonstrations have shown that applying insecticides to corn for worm control before tassel emergence does not produce better results than waiting until the usual tassel-emergence timing. Corn started under plastic or row cover is an exception to this rule.
Fields started under plastic or row cover will be most attractive to egg-laying moths because the plants are larger than those in bare ground fields. We have found that 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 from those moths. ECB eggs require 100 degree days (base 50) from oviposition to hatch.
Bare ground fields should be first scouted for ECB and FAW 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 very 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.
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 estimate of the number of infested plants.