Published on 02/20/03

Abetting bugs' battles can benefit farm crops

By Brad Haire
University of Georgia

They are covert operatives with code names like big-eye, lace wing, lady beetle and pirate. They're not military, but they are hungry. And they secretly fly, crawl and hop through farmers' fields, eating insects and worms that eat their crops.

Beneficial insects don't get the credit they deserve for providing cheap, environmentally safe control of crop-damaging insects, said John Ruberson, an entomologist with the University of Georgia College of Agricultural and Environmental Sciences.

"You will rarely see (beneficial insects) doing their thing," said Ruberson, who mainly conducts research on cotton insects. "After they're through, they tend to disappear quietly back into the field."

Who's hungry?

That cotton field you drive by during the summer may seem quiet and peaceful. But it's not. It's a battle field between the hungry and the hungrier.

Worms, like the cotton bollworm, tobacco budworm and beet armyworm, are major enemies of cotton farmers. These worms are eating machines, and they love to feast on the cotton plant. And the damage they do can seriously reduce yields.

However, just as the worms love to eat the cotton leaves, the "good bugs" love to eat the worms. In some cases, if left unfettered, these beneficials can help farmers knock out the worms without the use of insecticides, Ruberson said.

"You may get a lot of pest eggs, but the caterpillars that hatch from them may not reach a treatable level because things are eating them," he said. "We've seen untreated cotton do perfectly well throughout the season without much yield damage."

Better control

In the past decade, genetically engineered cotton has been used to control worms in cotton through a virus only toxic to the worms. Last year, about 55 percent of Georgia's cotton was genetically engineered. This has reduced the amount of insecticides needed for cotton pest control in this type of cotton and allowed more beneficial species to survive.

Traditionally, though, U.S. farmers must spray insecticides to control worms in their fields when they do get out of hand. It can vary from year to year, but Georgia farmers spend around $30 million each year to control pests in their fields.

Good with the bad

But insecticides aren't very selective. They kill the harmful insects, but they also wipe out the covert, beneficial bugs, he said. That's a shame.

Cotton worms usually invade fields for the first time each year around June. Some cotton farmers tend to reach for the insecticides around this time to protect against the invasion.

But farmers should hold back, Ruberson said, on that first, blanket insecticide spray.

Cotton plants can usually recover from worm damage that early in the season, he said. But it's hard for the beneficial insect populations to recover from it.

As many as 90 percent of most beneficial insects die in winter. They need the spring and early summer to increase their numbers. If they have that chance, a farmer could see the benefits later in the year.

Ruberson said new, more selective insecticide tools are coming into the marketplace. These tools, along with better management practices and understanding of how insects act, will help sustain Georgia's cotton industry while making it more friendly to the environment.

"Really, the overall goal of this type of research is to make our (Georgia) cotton an economically viable crop to grow," he said.

Beneficial insects can help do this by doing what they do naturally, he said, without the farmer doing anything.

Brad Haire is the former news editor with the University of Georgia College of Agricultural and Environmental Sciences.