Managing aphid populations in Mid-South cotton has become increasingly complicated in recent years. The advent of Bt cotton has altered the pest spectrum considerably, pushing aphids to the forefront of economically significant pests.
Increasing aphid pressure has meant more spraying, which has led — not surprisingly — to problems with resistance. The cycle has become increasingly difficult to manage.
It's not all doom and gloom, however. Intruder, a new product from Aventis CropScience, promises some relief, and the timing couldn't be better as far as researchers are concerned.
“Aphids are becoming more common, especially in conservation tillage production systems” says Roger Leonard, entomologist with LSU AgCenter's Macon Ridge Station. “As growers use seed treatments, they're building up faster in the field. In addition, the pyrethroids and some of the other insecticides we've been using to control plant bugs seem to be flaring aphids, and we're certainly not controlling them adequately with those same classes of chemistry.
“Resistance in aphid populations is currently an issue with most of the organophosphates and carbamates, with the exception of carbofuran,” he says. “Being able to change chemistry would be a very important benefit for aphid control because it would help us deal with some of these resistance issues more effectively.”
Intruder is a newer neonicotinoid chemistry that has received federal registration for use in cotton. Researchers at the university level have been evaluating the compound in field trials for several years. It is particularly effective against cotton aphids and also has activity against plant bugs and several other cotton pests.
“We've been looking at rates of Intruder from 0.025 up to 0.05 pound active ingredient per acre primarily for cotton aphid control,” Leonard says. “It is significantly better than Provado on cotton aphid and equal to Centric at the rates we've tested. It generally provides cotton aphid control equal to Furadan.”
Gene Burris, entomologist with Louisiana State University's Northeast Research Station, has noted similar results in his trials. “Intruder has been very impressive,” he says. “In fact, it's been one of the only products that's competed directly with Furadan. We still use Furadan on a Section 18 basis, but we would certainly prefer to have something with a better tox package that would be safer to handle.”
The Section 18 that has enabled growers to use Furadan in the past is re-evaluated each season. In addition, Furadan currently requires a 14-day re-entry interval.
“We need alternatives that we know are going to be available,” Burris says. “Even though we've been able to use Furadan in the past, the restrictions and re-entry period make it somewhat inconvenient to use.”
One of the primary advantages of Intruder will be its fit into Integrated Pest Management (IPM) programs. The product is easier on beneficials than some of the currently used insecticides. Burris says IPM is something the university has been touting for years, but in reality, it's not always practical.
“If you have to treat for aphids early, there's a lot of disruption of beneficial insects with a broad-spectrum insecticide,” he says. “With all the Bt cotton we have, we need to get away from those kinds of applications so we can take better advantage of the IPM tools that we already have. Intruder gives us an opportunity to implement a much more workable IPM program.”
Effective aphid control is one of the keys to implementing a successful IPM program. “The pest spectrum in this area has been changing,” Leonard says. “We're planting better than 80 percent of our acreage to Bollgard in Louisiana, and we're seeing a shift in pest problems away from the tobacco budworm/bollworm complex to the bug complex. That would include insects like the tarnished plant bug, the Southern green stinkbug, brown stinkbug, and cotton aphids. This is an ongoing process. We're not to the point where the shift is over. I think we're going to see some other pest problems emerge as well. Controlling aphids is one of the keys.”
Aphid infestations in the Mid-South tend to impact the critical fruit-setting period, which can have a significant impact on yield. “Aphids generally reach peak numbers in this area by mid to late June,” Burris says. “They usually cause a lot of leaf curl and stunting of the plant, and they impact the terminal growth.”