Thrips, nematodes bad duo for Carolina cotton growers

Less than 20 percent of cotton fields in the Carolinas have yield-limiting nematode populations and all early planted cotton is highly susceptible to thrips. When the two come together, it is a big problem for growers.

In 2006 the upper North Carolina-southern Virginia Cotton Belt was ‘thrips central’ and combined with nematodes the damage from these two tiny pests took a healthy bite out of cotton yields from South Carolina to central Virginia.

Though the two pests often occur together, they are traditionally managed by different chemicals and require additional time, labor and costs. Entomologists and plant pathologists at North Carolina State University have combined to look for some common ground to fight these pests.

One option for dual control, says Steve Koenning, a plant pathologist at North Carolina State University, is Temik at 5-7 pounds per acre, plus Vydate. This combination has worked well in some areas of the country, but not in others. In the Delta, growers have seen good results from the combination in about one year out of three. “That level of results makes it tough for us to recommend it in North Carolina,” Koenning explains.

Telone at 3-6 gallons per acre or Vapam are other options for nematode control in cotton. Koenning says research shows that two gallons of Vapam is equivalent in control to one gallon of Telone. Telone costs about $12 per gallon and Vapam cost $4-$5 per gallon.

Vapam may require some specialized equipment for application. Plus, Vapam is tough on metal equipment, so it may require more frequent changing of applicators. The extra cost of applying Vapam should be a consideration when comparing the total cost of the two soil fumigants for use for nematode control in cotton.

With either Telone or Vapam, growers will need to include an insecticide or plant insecticide treated seed to control thrips. Though these soil-applied fumigants may provide better control of nematodes in cotton, they provide no protection against thrips or any other insects.

The other half of the destructive tiny duo — thrips appeared in near record numbers across the northern one-third of North Carolina and southeastern Virginia. The corridor has been dubbed “thrips central’ for good reason, says North Carolina State University Entomologist Jack Bacheler.

Hopefully, everyone who planted cotton in this area either used a seed treatment or Temik. If a seed treatment was used, it should be clear by now that a foliar spray is also needed for full season control, Bacheler says.

The use of Orthene or similar foliar insecticides at the first true leaf stage, or about three weeks after planting is critical to thrips management, Bacheler says. “We have good research evidence that shows after three weeks, within a few days you might as well not have anything on your cotton plants for thrips,” he warns.

Seed treatments with an insecticide, plus Orthene at a quarter of a pound rate, applied at three weeks after planting provided similar results to Temik, the North Carolina researcher says.

If the seed treatment, plus Orthene system is well-timed, it should be comparable to Temik at five pounds per acre, according to Bacheler.

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