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Corn+Soybean Digest

BUG Zappers

Effective chemicals that go easy on beneficials An insecticide doesn't have to wipe out every bug when there's a seasonal or emergency outbreak of damaging pests. Joe Reed and other growers would just as soon leave the beneficials unharmed while the troublemakers are eradicated.

That's why Reed, a Kress, TX, cotton, corn and wheat grower, was eager to see results of so-called "environmentally friendly" pesticides tested on his cotton. And facing the worst beet armyworm outbreak in 20 years, he and others are eager to have new tools for corralling bugs before they chomp at leaves or bore into bolls.

One such insecticide appears to be spinosad, used in Tracer from Dow AgroSciences. It has provided strong bollworm (corn earworm) control in tests by Ivan Kirk, a USDA-ARS researcher at College Station, TX. It also demonstrated good armyworm control on Reed's farm and other areas of the southern Texas Panhandle.

Conducted in cooperation with Dow Agro-Sciences, Kirk's studies established that spinosad is less toxic than many standard insecticides to beneficial insects such as lady beetles and pirate bugs.

"It was reasonably effective on both bollworms and tobacco budworms, which also harm cotton production," says Kirk. "There was also less harm to beneficials than with other pesticides."

Reed's farm, about 500 miles northwest of Kirk's research area, was the host for studies by Greg Cronholm, a Texas A&M University integrated pest management agent.

"The ultimate goal is to make cotton, and when you spray to kill bugs harmful to the crop, there is often a risk of killing beneficials as well as bollworms or armyworms," says Reed. "We use an IPM program and do what we can to keep our beneficials. We welcome studies like those Greg is running."

Cronholm compared Tracer and several other insecticides, namely Confirm from Rohm & Haas, Denim from Novartis, Steward from DuPont and Intrepid from Rohm & Haas.

"Actually, all of these products seemed to be fairly light on the beneficial population, while providing good control of beet armyworms," he says.

Cronholm sees a possible advantage of Tracer for bollworm control.

"Tracer can be used at lower rates than some other chemicals," he says. "For some other chemicals, a pyrethroid may be needed for bollworm control. And pyrethroids also kill beneficials."

ARS's Kirk used aerial applications of spinosad in his bollworm-budworm research. The chemical was best applied in a 200-mm droplet size at a rate of 5 gallons/acre.

"Commercial cotton treated at this level had fewer damaging bollworm and budworm larvae compared to cotton treated with other pesticides," says Kirk. "Larvae found on cotton treated with standard insecticides were more mature, suggesting that spinosad prevented small larvae from becoming larger and more damaging."

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