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Nematodes pose serious threat to West Texas cotton

Lamesa, Texas, cotton farmer David Warren knows nematodes can eat his lunch. “I took in some new farms three years ago,” Warren recalls, “and yields the first year were way off. I made one and three-fourths of a bale per acre, but, considering the amount of fertilizer and water I put on, I expected better.”

He figured nematodes were the difference. “I added five pounds of Temik the next year and made 2.85 bales per acre,” he says. “Admittedly, we had better rain, but the water did not make all the difference.”

He switched varieties, too, to Stoneville 5599 BR, which has shown tolerance to the root-knot nematode, which may be taking more cotton away from West Texas farmers than they realize, especially if they farm sandy ground.

“Nematode control was the key to improved yields,” Warren says. “Most of my cotton is in sandy soil, so I sample most fields for nematode infestations every year. Some have heavier infestations than others.”

He says many of his cotton fields show only spotty infestation, sometimes a circle that’s stunted or less vigorous than the rest of the field. “But even with spots, yield losses can be significant.”

Warren was looking at a new product on test plots this year, Syngenta’s Avicta Complete Pak, a three-pronged combination of nematicide, insecticide and fungicide, applied as a seed treatment.

“I can’t see any difference yet,” he says. “I’ll wait until harvest to see how it does.”

Peanuts as rotation

“Nematodes are all over this part of the world,” says Chuck Rowland, who farms cotton and peanuts in nearby Gaines County. “We’ve been able to get by without too much yield loss with rotation and Temik. Peanuts really helped us as an excellent rotation crop.”

A species of root-knot nematode infests peanuts but it’s different from the southern root-knot that can take a heavy toll on cotton.

“Cotton farmers in this area (mostly sandy soils south of Lubbock) will need to pay more attention to nematode problems,” Rowland says.

Terry Wheeler, Texas A&M research plant pathologist and nematologist, discussed the problem during a recent Syngenta plot tour (which included Warren’s farm). She says 40 percent to 45 percent of the area’s cotton soils have root-knot nematode infestations. Symptoms may be subtle, she says.

“In sandy soils, the crop may appear uniform because nematode populations are fairly consistent throughout the field.”

Growers may be losing pounds without realizing the cause, she says.

“Nematode populations are dynamic. They continue to build year after year. With a peanut rotation, farmers may have no problem the following growing season, but they need to do an assay the next year, after cotton, to determine population levels. Some fields lose a significant percentage of yield to nematodes.

Monitor population

She says growers in a nematode-prone area may not need to pull samples every year. They pretty much know they have populations and should either rotate, use a chemical control or both. “But, even with a good rotation, growers need to monitor the population.”

She says a farm she’s checked using infrared imaging shows devastating yield losses to nematodes. “The grower has lost one circle of cotton and most of another one.”

Wheeler says cotton farmers need to rotate and provide some pre-plant protection. Temik has been the standard. “I’m eager to see how Avicta performs this year,” she says. One advantage of the new product is that farmers will not be tempted to cut rates and sacrifice control. “Also, seed treatments eliminate clogged tubes and inconsistent application.”

Wheeler says no resistant variety exists. “ST 5599BR is tolerant,” she says. “With heavy pressure, 5599 needs a nematicide. I don’t like to see other varieties go out (in infestation-prone areas) without protection.”

Wheeler says hail damage typically wipes out nematode populations.

Peanuts provide the best rotation option. “Southern root-knot nematodes are capable of reproducing on milo,” she says, “and sometimes build to high levels. Most everything else in the area, including weeds, is a host.”

She says anything that stresses a cotton crop may exacerbate nematode damage. “Thrips injury, for instance, enhances seedling diseases and nematode damage. Thrips control may be a key.”

Billy Hutson, with UAP out of Lewisville, Texas, says farmers who grow cotton in West Texas’ sandy soils “know they have nematodes. In other areas, with tighter soils, they may be learning about them. We know that treatment pays off.”

He says West Texas also has more cotton seedling disease than growers once thought they had. Nematode damage symptoms may include stunted plants, galled roots and overall poor performance.

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