Alabama study yields insights into reniform nematode management

A 10-acre field in a remote corner of southwest Alabama near Huxford comprises the frontline in the almost 20-year war against reniform nematodes.

“Historically, this is a very important location,” says William S. Gazaway, an Alabama Cooperative Extension System crop consultant and Auburn University professor emeritus of entomology and plant pathology.

It was here, for example, that Gazaway and other crop experts first discovered the serious cotton yield reductions associated with reniform nematode damage in 1987. But that's not all: The field, which was converted into an Auburn University research plot in 1989, has yielded valuable insights into the importance of rotating cotton with peanuts and corn to reduce nematode infestations.

“Peanuts, in particular, are an ideal rotation crop,” Gazaway observes — which is “why producers are growing a lot more peanuts in southwest Alabama, especially in Escambia, Monroe and parts of Baldwin and Mobile counties” where the problem is most severe.

Still, growers want to limit their rotation into peanuts as much as possible to capitalize on cotton profitability.

“Most cotton producers simply want to be in cotton as much as possible and would rather not rotate,” Gazaway says.

With this in mind, a major focus of the Huxford study in recent years is determining if cotton growers can squeak by with only a one-year rotation into peanuts, coupled with a judicious use of nematicides, such as Temik or Telone. Recently, Gazaway's fellow researcher, Kathy Lawarence, an Auburn University assistant professor of entomology and plant pathology, began looking at Avicta, a new seed treatment that, in addition to controlling nematodes, also addresses insect problems.

“Simply put, can we get by with only a one-year rotation or do we have to go up to two years to get the maximum benefit?” Gazaway asks.

While much has been gained from the rotation studies, Gazaway concedes a lot more fine-tuning remains, especially in determining how chemical treatments are best used to enhance the effects of rotation.

“I personally don't think we're there with the seed treatments — yet, at least,” Gazaway says. “They just don't compare with Telone or Temik.”

Likewise, Telone, despite its many advantages, has only limited application — an expensive product that is best suited to fields with unusually heavy nematode infestations. It also is unsuited to areas of the state where conservation-tillage is widely practiced, such as north Alabama.

Studies in which Telone has been applied using a Yetter rig yielded encouraging results, though more investigation is required, Gazaway says. Moreover, unlike Temik, Telone has no effect on early season insects.

“Temik is a lot cheaper, not only because you get nematode control but because you also pick up early season insects,” he says. “If you use Telone, you still have to use insecticides."

Still, in an effort to cut chemical costs, researchers are looking at ways to apply Temik more effectively. Recently, for example, Gazaway has revisited the practice of applying Temik as a banded treatment rather than into the seed furrow as is commonly done.

“It may be that we get additional benefit putting it into the band and working it in through water,” Gazaway says. “The basic premise behind nematode control is that the wider the zone the better.”

Whatever turns out to be the most effective approach, Gazaway believes the insights gained from the Huxford study could influence future rotation recommendations throughout the Southeast.

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