Cotton insect control a balancing act

“We're not oblivious to the potential of a budworm resistance problem. But we're more afraid of the alternative — creating armyworm problems that'll be difficult to control.”

In a scene that has become all too familiar, many cotton producers in the Florida Panhandle were planting their crops in bone-dry soils during May in the rush to meet crop insurance deadlines.

“Our planting has varied from one area of the state to the other,” says Richard Sprenkel, University of Florida Extension entomologist. “As of mid-May, most of the cotton had been planted in the western counties of Escambia, Santa Rosa and Okaloosa, where growers received rainfall near planting time.

“On the other hand, as little as 40 to 60 percent of the cotton had been planted in Jackson County, which has been our largest cotton producer for the past two years. Soil moisture levels dropped so rapidly that growers stopped dusting in the crop. They're just hoping to get some moisture before the crop insurance deadlines.”

Florida's total cotton acreage for 2001 should reach from 120,000 to 125,000 acres, assuming all planting intentions are met, says Sprenkel. “The cotton that already has emerged looks surprisingly good, but that's due mostly to early season moisture. Now, the crop is just sitting there,” said Sprenkel in mid-May. “We're seeing a combination of dry weather and very cool nights, and this results in more thrips problems.”

Florida cotton producers harvested about 90,000 to 95,000 acres last year, he says, with 10,000 to 15,000 acres being destroyed due to drought.

“There's just not much else here that's as profitable to plant as cotton, even with its current price problems,” notes Sprenkel. “But an increasing number of our farmers are cutting back on their acreage, and I'm not sure how they'll continue to manage.

“The expansion of cotton acreage in Florida has reached a standstill. I don't think there's much likelihood of us going past 120,000 to 125,000 acres.”

Recent cultural changes in Florida cotton production — including an increased use of strip-tillage and Roundup Ready varieties — have led to more pressure from insect pests such as cutworms and grasshoppers, says Sprenkel.

“Grasshoppers became a real problem last year, and we're already seeing signs of that happening again,” says the entomologist. “In Santa Rosa County alone, where they grow about 25,000 acres of cotton, producers treated about 10 percent of the acreage last year for grasshoppers.

“Grasshoppers lay their eggs in pods in the ground. If weather conditions are dry, the survival rate for the eggs improves and there are a fewer number of predators. We came off a dry year in 2000 and we're coming off another dry year in 2001. Grasshoppers laid their eggs last fall and they're now emerging. Some fields already have been treated.”

Sprenkel anticipates that as the cotton crop progresses, growers will see more plant bugs in their fields, including tarnished plant bugs and false chinch bugs. Identification samples coming in from other crops indicate increased populations of plant bugs, he adds.

“Several years ago, we had a problem with cotton fleahoppers in Florida, and I wouldn't be surprised if we didn't get back into that cycle this year.”

Dry weather and a cotton crop that puts on any growth will be good conditions for plant bugs, says Sprenkel.

“Unlike in other areas, our plant bug populations still are very susceptible to control from pyrethroids and organophosphates. We don't have to be real careful about our choice of insecticides.

“Our main consideration should be what kind of problems we'll create later in the season by using these materials. If we're not careful, we'll have problems later on with the bollworm-budworm complex and with beet armyworms.

“I would lean more towards the pyrethroids because we don't have a bad problem in Florida with budworm resistance. We do know, however, that we can grow a good crop of armyworms. And if we do too much pyrethroid spraying early in the season — for thrips or plant bugs — we can create problems with beet armyworms, especially in dry weather conditions. I'm more concerned about beet armyworms than resistant budworms.”

When treating for thrips, growers should consider if conditions are favorable for beet armyworms, says Sprenkel. These conditions would include a mild winter, dry weather and the early season use of organophosphates. They also would include, to some extent, the use of pyrethroids, he adds.

“I wouldn't haphazardly treat for thrips. The granular materials used at planting and the new seed treatments work well on the regular flower thrips. Don't rely entirely on coming back over the top for thrips control. You'll create more problems for the future. And, it's difficult to keep up with the waves of thrips that come in during these weather conditions.”

The same strategy for controlling thrips and plant bugs also can be used for grasshoppers, says Sprenkel. “Essentially, we have the same choice of materials — we can use an organophosphate or a pyrethroid. Hopefully, you won't use too much of either one, and our preference would be to use a pyrethroid for early season grasshopper control.

“We're not oblivious to the potential of a budworm resistance problem. But we're more afraid of the alternative — creating armyworm problems that'll be difficult to control.”

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