Mississippi and Tennessee have revised their treatment thresholds in non-Bt corn. “We’ve gotten quite a bit more aggressive based on data. We’re also triggering more applications based on moth-trapping. It used to be ‘treat if 20 percent of your plants are infested.’ Well, our data shows that by the time 20 percent of your plants are infested, you’ve got yield loss.

“So, we’re saying to treat when first generation, whorl stage, 5 percent or more of your plants are infested with either eggs or small larvae.

“Or, if you run pheromone moth traps, treat when you’ve caught 50 or more moths in a week.”

After tassel up until R-3, a new recommendation is to treat when you have 10 percent or more infested plants. “It used to be about 20 percent. Really, we’re saying anytime you catch 100 or more moths per week during the crop’s sensitive stage, consider a treatment in the next four or five days.

“But the reality is the vast majority of our acres manage corn borers with Bt corn.”

What about the “old” Bt versus “new”?

“With the old Bt technologies – YieldGard, Herculex, Bt3 – if you’re in an officially-designated cotton-growing area, there’s supposed to be a 50 percent non-Bt refuge. In a non-cotton-growing area that refuge could drop to as little as 20 percent.”

As for the newer technologies, companies are putting in more traits. As a result “they’re getting redundant control of corn borers – built-in resistance management is the hope. Because of that, for most of the varieties in cotton- and corn-growing areas, the refuge requirement is reduced.”

It’s pretty simple in cotton-growing areas, said Stewart. “You can reduce the non-Bt refuge requirement to 20 percent.”

Meanwhile, in a corn-growing area, there are many options. “With some of them, you can go down to a 5 percent refuge. You can plant a refuge in a bad where the seed is mixed in. Some require a 10 percent refuge, depending on the traits. Some stick to 20 percent. Do your best, make an honest effort.”