But two Texas Agricultural Experiment Station entomologists think they can reduce these losses with a new model to predict and better target the pests.

The model developed by Dr. Jerry Michels, Experiment Station entomologist in Bushland, and Dr. Marvin Harris, Experiment Station entomologist in College Station, is based on temperature and number of adults emerged.

While crop rotation is the best way to control the corn rootworm, many corn growers don't have that option. So producers spray. Timing of the spray is critical, Michels said.

As much as 25 percent of the yield loss is from the adults clipping the silks, but the greater damage is done by the larvae, chewing off the roots of the corn and causing it to fall over, he said. As much as 75 percent of the crop can fall over.

"The idea behind this is to control more adults before the fall, so the number of eggs and resulting larvae the next spring will be lessened," Michels said.

He started collecting data on adult western corn rootworm emergence in 1996. Nine years of catching adult beetles in traps and comparing the data with temperature data from the North Plains potential evapotranspiration network helped the researchers determine emergence patterns.

"The emergence pattern of the beetles is quite variable for a given year," Michels said. "However, because it is temperature-driven, the model is flexible and can account for differences in emergence due to normal, cool or hot years."

This flexibility can improve Western corn rootworm management decisions by showing when an insecticide application will do the most good, Michels said.

The model has been incorporated into the North Plains PET weather station network. Daily model output can be accessed by going
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Contact: Dr. Jerry Michels
gmichels@ag.tamu.edu
806-354-5806
Texas A&M University - Agricultural Communications
8-Jun-2005