Texas Boll Weevils Beware: A New Parasite Is in Town

The traditional foe of cotton plants has become more resistant to pesticides, so government scientists have declared biological war

EVERY year, American cotton growers lose about $300 million because of a small insect with a big appetite.

But now, the hungry boll weevil may become a feast itself.

Scientists from the US Department of Agriculture say they have found a way to raise tiny parasites that dine on weevil larvae. After field tests, some Texas farmers are calling the bug the greatest thing to hit the cotton industry since denim.

The parasite, known as Catolaccus grandis, has a leg up over its competition in the war on weevils. Unlike the expensive chemical pesticides currently used, the one-eighth-inch-long Catolaccus is proving to be more effective and doesn't wipe out beneficial insects that keep other pests under control.

''It definitely could be the solution for the boll weevil,'' says Ralph Hoelscher, a cotton farmer in San Angelo, Texas, who took part in field tests last fall. ''It worked well, like 95 percent control or better. Traditional pesticides give control of 75 to 80 percent, at the best.''

Interest in the Catolaccus has surged in Texas after last year's catastrophic cotton harvests in two regions that were attempting to eradicate the weevil. Many farmers blamed the poor crop on the program of the Texas Boll Weevil Eradication Foundation, a quasi-governmental agency. Under the program, some farms sprayed malathion a dozen times in an effort to wipe out the weevil. To be sure, the weevils died, but the spraying led to an invasion of the beet armyworm, another cotton pest. The armyworm cost farmers $300 million in Texas alone. Last month, farmers along the Rio Grande voted almost 3 to 1 to halt the eradication effort in that region.

Heavy pesticide use - including the application of malathion - was ''the primary causal factor for the beet armyworm outbreak,'' wrote USDA scientists K.R. Summy and J.R. Raulston in a preliminary report.

''The cotton plant provides a smorgasbord for a wide variety of insect pests,'' says Gary Herzog, a cotton pest entomologist at the University of Georgia. ''What makes it worse is that the fruiting period for cotton occurs over such a long period of time.''

In normal years, cotton farmers spend up to $40 per acre per year on insecticides. But as the demand for casual clothing has surged since 1980, US cotton production has nearly doubled and more cotton means more opportunity for pests. According to the National Cotton Council, farmers in the Cotton Belt spent nearly $59 per acre on insect control last year, an increase of almost 50 percent.

Farmers have found that while chemical pesticides kill weevils, they also kill the beneficial insects that keep other cotton pests under control. By using the parasite, farmers could avoid spraying their fields in the spring, when the beneficial insects begin to reproduce. The parasite also offers a viable solution for organic cotton farmers like Mr. Hoelscher, who have struggled for years to find an effective organic weevil control system.

The Catolaccus is still an expensive beast to produce on a large scale, but scientists at the USDA's Subtropical Agriculture Research Laboratory in Weslaco, Texas, are starting to find ways to bring down that cost. They recently devised an artificial diet for the Catolaccus, which cut their costs by more than half.

The lab also received a boost from a Department of Energy lab in Kansas City, which developed machinery to raise enough parasites for testing on Hoelscher's farm. Now, the DOE and USDA are working with private industry to find cheap ways to raise Catolaccus on an industrial scale.

One such company, Integrated BioControl Systems Inc. of Lawrenceburg, Ind., plans to produce enough parasites by 1997 to treat 10,000 acres of cotton.

Company president Jim Cate says the parasite is not a ''silver bullet solution for the weevil.'' But he says cotton farmers will have to adopt more biological controls like the Catolaccus if they want to continue raising cotton. ''The weevil is getting resistant to pesticides,'' he says. ''And it's getting to the point where farmers won't have many other options.''