The recommendation is for producers to wait until they see about 50 percent emergence, he said. Because residual of most of the chemicals is a week to two weeks, a producer would miss a large part of the population by spraying too early, Michels said.
"We can control adults and if we get rid of enough of them, it will lessen the impact," Michels said. "If we can have a model to tell our producers when we have about 50 percent adult emergence, the producer can make an application at that time."
Over the years, he said, the model is showing 50 percent emergence can come anytime from July 13 to Aug. 15.
"If it is a hot year, emergence will be earlier than a cool year," Michels said. "So rather than saying we need to spray on July 15, some years it might need to be delayed."
"We feel this is a robust model," Harris said. "We think of this physiological model as providing us a bus schedule.
"When we have the bus schedule saying 25 percent of the adults will be out and active, we can go to the field and meet that bus and actually census the number of adult beetles there," he said.
A field census of beetles represents about one-fourth of what is actually there, Harris said.
"If the number is significant enough, we institute management. It lets us orient in time to make management decisions," he said. "When we incorporate this to overall management, we will limit pesticide usage to when it is needed."
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Contact: Dr. Jerry Michels
gmichels@ag.tamu.edu
806-354-5806
Texas A&M University - Agricultural Communications
8-Jun-2005