Reniform nematodes pose threat to High Plains cotton production

High Plains cotton farmers can add one more item to the list of problems they face.

Infestations of reniform nematodes (Rotylenchulus reniformis) have shown up in Floyd, Lamb, Lubbock, Lynn, Terry, and Hockley counties. The highest levels of infestation are in Lubbock and Lynn counties.

“Unfortunately, distribution of this pest is on the increase,” says Terry Wheeler, plant pathologist with the Texas Agricultural Experiment Station at Lubbock. “Once reniform nematodes get established in a field, they cannot be eradicated.”

These nematodes survive in soil for years and are easily spread by cultivation. They can be carried to other fields in soil clinging to farm equipment, vehicle tires, and footwear. Drainage water also can spread them.

“Symptoms of reniform presence include plant stunting and reduced yields. However, these symptoms also can be the result of nutritional deficiencies and other problems. Therefore, only examination of soil samples by a properly trained person can confirm the presence or absence of reniform nematodes,” Wheeler said.

“If producers want to get a good estimation of the extent and severity of their nematode problem, they must take a sufficient number of soil samples in an acceptable manner. I recommend the following procedure:

-Sample anytime from June through the following April.

-Do not sample if air temperature is below 40 degrees Fahrenheit.

-Take samples from a minimum of three areas within each 120 acres.

-Go into the first area and dig a hole 4 to 12 inches deep adjacent to a plant. (The later in the season, the deeper the sampling should be as nematodes migrate downward as the soil gets colder.)

-Take a handful of soil within two inches, or less, of the taproot and place it in a bucket.

-Take about 20 paces within the area and repeat the sampling procedure.

-Repeat these steps until 15 to 20 samples from the first area have been taken.

-Thoroughly mix the soil in the bucket, remove about one quart of soil and seal it in a moisture-proof bag to prevent drying.

-Label the sample appropriately and immediately store it in a cool place.

-Repeat the above procedures in areas two and three.

-As soon as possible take the three samples to A and L Plains Analytical Laboratories in Lubbock or to the Texas Agricultural Experiment Station (1102 East FM 1294, Lubbock, TX 79403).

“Yearly chemical treatments and every-other-year rotations with sorghum, corn, or peanuts can increase lint yields substantially,” Wheeler said. “The reniform nematode reduces yield by approximately 50 percent in a good year and 80 percent to 90 percent in a bad year. Chemical control with Temik 15G, Vydate, or nematicide seed treatments may return only about 10 percent of that yield loss. Crop rotation should improve yields much more than chemical control, except for fumigation. Fumigation provides the best yields.

“Telone II (a fumigant) applied at 5 gallons per acre has given us good reniform control. It should be injected approximately 20 inches deep in the center of the seedbed and the slit covered immediately.

“Temik 15G gives good reniform control at 3.5 to 5.0 pounds per acre. But for this chemical to work properly, the soil needs to be moist as the nematodes must contact the nematicide in solution in the soil.” Wheeler said.

Vydate is a liquid systemic insecticide normally used in conjunction with a preplant application of Temik 15G or a nematicide seed treatment. It is generally applied to plants at the pinhead-size-square growth stage and two weeks later if nematode infestation is quite high.

“Nematicides for seed treatments include Avicta Complete Pack and Aeris. These are more expensive than Temik 15G (at 3.5 pounds per acre) and are not always as effective. But they are more convenient, and less hazardous to handle,” Wheeler said.

Wheeler has some encouraging news. “Genes for resistance to reniform nematodes have been transferred from an exotic cotton species into upland cotton lines. Within a few years acceptable reniform-resistant varieties should be available.”

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