Published on 07/15/96

Secretive Bug Withering

Drought symptoms seem unmistakable. Withering, brown and poorly developed plants all point to a lack of water. But a tiny insect is fooling Georgia farmers.

"We estimate 10 percent to 15 percent of Georgia's 400,000 acres of soybeans may have significant infestations of lesser cornstalk borers," said Randy Hudson, an entomologist with the University of Georgia Extension Service. "Nearly one-quarter of this acreage could have severe losses."

Soybeans provide much of the protein meal used to feed livestock including hogs, cows and chickens. A drop in the meal supply could cause an increase in feed prices and finally an increase in retail prices for many meats.

Hudson said the drier fields get, the worse the lesser cornstalk borers will be. "Their damage mimics drought stress," he said. "The plants wither, turn brown and eventually die."

A soaking rain, he said, will help control these destructive larvae.

The problem is, many farmers may see only drought stress in their fields and wait for rain to improve their crop. But if the insect is out there, just a little rain won't help at all, Hudson said.

Lesser cornstalk borers feed on plant roots just below the soil surface, damaging the root system where it takes up nutrients and water. They'll infest corn, grain sorghum and millet, too. But they have a taste for soybeans, especially late- planted beans.

Georgia farmers planted about 25 percent of this year's soybean crop behind another crop, usually grains. And about 30 percent is considered "late-planted." These fields are most susceptible to lesser cornstalk borers.

"These fields could sustain up to 75 percent yield losses," Hudson said. "That's a potential loss of more than $20 million."

Early July brought soaking rains, the best remedy for the problem, for some farmers. Where infested fields are still dry, growers can kill the hungry larvae with insecticides.

Hudson said chemicals are costly, but in fields where they're needed, they'll pay off for farmers. "We're seeing soybean prices up near $8 per bushel this year," he said. "We can't afford to lose out on that opportunity."