Crop-threatening levels of root-knot nematodes (RKN) are present in some cotton fields in southeast Missouri. The symptoms of RKN injury will initially be visible 6-8 weeks after cotton emergence and may include yellow-green leaf color, stunt, and these plants may wilt more quickly than healthy plants during a hot afternoon. Plants injured by these nematodes will have swollen areas, galls, visible on infected roots 6-8 weeks after emergence. Farmers and/or consultants should be cautious about diagnosing the cause of yellow-green leaf color and stunt of midseason cotton because other factors such as low soil pH and drought may cause this, but only RKN causes galls on roots.
Cotton farmers can take action to protect their crop against these nematodes during 2009, but their options are limited. There are no cotton varieties highly resistant to RKN although some varieties are more resistant than others. Growers should consider using a nematicide such as Telone prior to planting, Temik at planting, or a seed treatment such as Avicta or Aeris. The crop may be sprayed with Vydate a few weeks after emergence for nematode suppression, but a nematicide such as Temik should have been applied at planting. There are advantages and disadvantages to the use of each of these products.
Following these suggested procedures will give cotton farmers a better chance of producing higher yields and greater profits in 2009. For more information contact Allen Wrather at the University of Missouri Delta Center (Phone: 573-379-5431, E-mail: firstname.lastname@example.org) or check the Delta Center Web Page (aes.missouri.edu/delta).
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REVISED: August 2, 2012