New Bt corn technologies coming out over the next few years will help southern growers reduce refuge acres and manage resistance, but the jury is still out on what yield benefits might be expected.

One of those new technologies, YieldGard VT Triple Pro, will be available in 2009. It contains two corn borer toxins, one corn rootworm toxin and Roundup Ready 2. There will be limited seed supplies available this year.

SmartStax technology, which will likely be available in 2010, has three Bt corn borer traits, three Bt rootworm traits, plus Roundup Ready 2 and LibertyLink technologies.

Other companies, including Syngenta (Viptera) and Bayer CropScience, are also pursuing stacked Bt corn traits.

The new technologies do the job, said Scott Stewart, Extension entomologist with the University of Tennessee, speaking at the Tennessee Grain and Soybean Conference in Dyersburg, Tenn. “I’ve looked at the SmartStax and the YieldGard VT Triple Pro for a couple of years, and I can tell you, they are much better at controlling corn earworm and are a big improvement in controlling fall armyworm.”

Despite the improved insect control, Stewart has not seen a yield benefit from the technologies in his research plots, “even though we’ve had pretty good earworm pressure. There’s some value in it in terms of being able to plant more of it by reducing the refuge, and there are some resistance management values.

“This is a pretty limited data set right now, and once we get some more data, I might change my opinion. But for now, it won’t be sold so much on yield enhancement as risk management.”

Stewart noted that current technologies containing Bt proteins are excellent on corn borers, “so it’s kind of hard to improve on near perfection.”

Stewart noted that much improved control of corn earworm and fall armyworm with advanced Bt technology “could lower the chance of Bt resistance in corn earworm. And there may be some potential benefits in reducing aflatoxin. Insects aren’t the main factor in aflatoxin, but they are a stress factor that can increase the risk.”

When the adoption of SmartStax and YieldGard VT Triple Pro occurs, “it’s going to reduce the magnitude of our bollworm/corn earworm flight coming from corn,” Stewart said. “One of the biggest benefits in terms of insect management could be on other crops like soybeans and cotton.”

Stewart said producers growing non-Bt corn or white corn or popcorn in middle Tennessee, “need to be managing southwestern corn borer. One thing you really need to do is run pheromone traps. They are very diagnostic as to whether you have the potential to have a problem.”

“On a moderate infestation of southwestern corn borer on a late-planted field in 2008, one well-timed insecticide application increased yields as much as 40 bushels per acre. But you have to manage for this insect and you have to know it’s out there.”

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