Planting Bt corn along with standard hybrids helps growers combat southwestern corn borers that can be a serious problem in the western part of Kentucky. However, growers should consider several factors before adding Bt corn to their farming operations.

"Growers using Bt corn also should plant standard hybrids to establish refuges to sustain a population of southwestern corn borers. This helps Bt corn maintain its effectiveness by slowing the development of corn borer resistance. Using a refuge of standard hybrids with Bt corn makes good economic sense," said Ric Bessin, Extension entomologist with the University of Kentucky College of Agriculture.

"Bt corn should not exceed 70 to 80 percent of a grower's corn acreage," he added. "This means 20 to 30 percent of the acreage should be dedicated to standard hybrids."

Growers should consider the planting date and economic factors when deciding whether to use Bt corn, according to Bessin.

"Late planting, say after May 1-10 in western Kentucky, predisposes standard hybrids to problems with southwestern corn borers," he said. "So the date you get corn into the field is one factor to consider when evaluating Bt corn for your particular operation."

Other factors to consider are the cost of Bt corn, grain prices and the uncertainty of how serious corn borer problems will be this season, according to Bessin.

"Bt corn isn't cheap," he said. "It costs about eight dollars an acre more than the standard hybrids. But if you have corn borers, it's definitely worth the price. A lot depends on insect pressure. For example, a population of two corn borers per plant could lower yields as much as 10 bushels, or $20 per acre.

"Just because 1998 was a bad year for corn borers doesn't mean 1999 will be bad as well. With low grain prices, growers should limit planting Bt corn to situations where it likely will pay for itself."

Bessin said growers are showing an incredible amount of interest in Bt corn.

"We might see a 50 to 60 percent increase in Bt corn in many counties this year, due largely to the high southwestern corn borer populations in the 1998 crop," he said. "The mild winter during the 1998 growing season contributed to these large populations."