Even if you haven't planted Bt hybrids before, you may want to consider them for 2000. They could pay off big, predicts a farmer who plans to increase his Bt acreage.

"We see Bt corn as an insurance policy," says Brad Smith, a farmer and seed dealer at Milledgeville, IL. "In seven years out of 10, we have enough corn borer pressure that Bt corn will more than pay for itself. That means we will cash in on the insurance policy 70% of the time.

"We have had relatively light corn borer pressure the past two years and, to me, that indicates the odds go up considerably for heavy pressure in 2000," says Smith, who farms with his father, Steve.

The Smiths planted 40% of their corn acres to Bt hybrids in 1999 and plan to boost that to 70% for 2000.

"The fact that some Europeans don't want to buy our genetically modified crops is something we have to consider when we select what to plant," says Smith. "However, we need to remember that the vast majority of U.S. corn is fed to livestock and poultry in this country, and is not exported."

The biggest thing to keep in mind about European corn borers is that they're unpredictable, points out crop consultant Mark Kottmeyer, Kearney, NE.

"Our area is largely continuous corn, so we have scouted fields and then sprayed for corn borers if the numbers were above the economic threshold," Kottmeyer notes. "Our average treatment requirements over 15 years have been 19% for first generation and 38% for second. But it has fluctuated from no treatment to 94%." Corn Belt entomologists report that spraying typically provides 60-95% control of first-generation borer larvae and 40-80% of second-generation larvae. In contrast, Bt hybrids with full-season protection provide 95% or better control of both generations.

If a farmer is buying only a limited amount of Bt corn, Kottmeyer recommends that it be in longer-season hybrids. They take longer to mature and therefore are more susceptible to second-generation borers.

Even though corn borer pressure was generally moderate in 1999, there were pockets with significant damage.

"In northern Illinois, for example, the first generation was very light," reports Scott Stein, agronomic systems manager for Monsanto at Dekalb, IL. "But there were noticeable to significant infestations of second-generation borers." Stein points out that an increasing area of the north-central Corn Belt appears to be seeing both bivoltine (two generations per year) and univoltine (one generation per year) corn borers.

"The univoltine comes between the two flights of the bivoltine and therefore we are seeing an almost continuous flight of moths," Stein notes.

"This makes scouting and then treating by conventional means more difficult."