Bugs Take Bite Out of Georgia Cotton Crop

By for CAES News

Boll weevils don't bother Georgia cotton anymore. But farmers still have to battle insects. In fact, University of Georgia scientists say bugs have already taken a big bite out of this year's cotton harvest.

"It's still too early to tell how much we've lost to insect damage," Phillip Roberts said. "We've probably lost more than in the past few years."

Roberts, an Extension Service entomologist on the Tifton, Ga., campus of the UGA College of Agricultural and Environmental Sciences, said cotton crop losses are hard to estimate now. The Georgia harvest won't start until mid- to late September.

"It's easier to assess the money farmers have spent trying to prevent loss," Roberts said. "On average, they've sprayed non-Bt cotton four-and-a-half to five times. And they've sprayed Bt cotton one to one-and-a-half times." The number of sprays varies from field to field, ranging from none to 10.

Bt cotton is a type genetically engineered to contain a bacterium, Bacillus thuringiensis, that attacks bollworms. Georgia farmers planted Bt cotton in nearly 40 percent of their 1.44 million cotton acres.

Pesticide sprays cost about $9 per acre. Going into the last week of August, they had cost Georgia cotton growers $41 million to $47.5 million.

The main cotton pests have been corn earworms, tobacco budworms and fall armyworms. Farmers have long lumped the first two together, calling them bollworms. But in the past two summers, they've had more problems with corn earworms than in the previous several years.

Bt cotton doesn't control corn earworms as well as it does tobacco budworms. It has little effect on fall army worms.

"And we've had the worst fall armyworm outbreak we've had in several years," said David Jones, an extension entomologist in Statesboro, Ga.

Roberts and Jones both say they've seen a troublesome change in corn earworms' behavior this year. In a sense, they're getting smarter.

"We're finding the moths laying eggs lower in the plant canopy," Roberts said. "That has been happening for years and years, but the frequency is increasing." Caterpillars low in the plants are harder to kill, since pesticides are sprayed over the top.

Farmers control insects with a system called integrated pest management. IPM scouts check fields often for insect pests. Only when the pests reach a certain population will farmers spray cotton fields with a pesticide.

"We've had a tough insect year," Roberts said. "We've still got a quality cotton crop. But we've had to spend more money on it."

How bad has it been? "Several of the leading chemical companies' pyrethroid insecticides are sold out," Jones said.

Heading into the last week of August, "egg counts shot up tremendously," said Jones, who works mainly in east Georgia. "We were seeing egg counts of 100 in many fields. In other words, if a scout checked 100 plants, he'd find 100 eggs on them."

Jones urged farmers to check their fields closely. "We still have extreme insect pressure in some fields," he said. "And we don't have much longer to make cotton."

In most of the state, he said, the bollworm and fall armyworm cycles are winding down. But populations in some fields are still high. And farmers still have a potential problem with soybean loopers, which feed on cotton foliage in late August and early September.

Stinkbugs, he said, are damaging cotton, too. He tells scouts to check closely for them by shaking the plants over a dropcloth spread between the rows.

"Stinkbugs are an unseen pest," Jones said. "They suck the juices out of the seeds inside the bolls. They cause damage now, but you don't see it until later."

Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.