Cotton: U. of Missouri tells growers to be aware of root-knot nematodes

Doane posted the following advisory on our content site this afternoon:

6/2/2006 -- Crop-threatening levels of root-knot nematodes are present in some, but not all, cotton fields in southeast Missouri, says Allen Wrather, University of Missouri professor.

During a recent survey of Missouri cotton fields by University of Missouri scientists, root-knot nematodes were found in 20 percent of the New Madrid County fields, 27 percent of Pemiscot County fields, and 43 percent of Dunklin County fields. This nematode is also present in some Scott County fields.

These nematodes can cause severe injury to cotton and will reduce yield. The symptoms of root-knot nematode injury will initially be visible 6-8 weeks after planting. Most years, the symptoms are visible during early- to mid-June.

Unfortunately, cotton planting this year has been delayed for some producers due to wet weather and symptoms may not be visible until late-June to early-July. The symptoms of root-knot nematode injury are stunted cotton plants and these plants may wilt more quickly than healthy plants during a hot afternoon. Plants injured by these nematodes will also have galls; swollen areas visible on infected roots.

Be cautious about diagnosing the cause of stunted cotton, because other factors such as low soil pH and drought may cause plants to be stunted. Ask your scout to tell you about areas in your fields where they observe this symptom and then determine the cause of the stunting.

Growers suspicious of nematode problems in their cotton should dig up roots soon after harvest and the stalks are shredded and look for galls on the roots.

Nothing can be done this year to protect cotton against these nematodes, but growers can take precautions to avoid this problem next year. There are no cotton varieties highly resistant to root-knot nematodes, but Stoneville 5599 is tolerant. These nematodes will reduce yield of this variety but not as much as they reduce yield of other varieties.

Growers should consider planting Avicta Complete Pak treated seed or using Temik at 3.5-5.0 pounds per acre in furrow when planting this or any other cotton variety.

Following these suggested procedures will give cotton farmers a better chance of producing higher yields and greater profits.

For more information contact Allen Wrather at the University of Missouri Delta Center (Phone: 573-379-5431, e-mail wratherj@missouri.edu or check the Delta Center Web page.

The University of Missouri-Delta Center Field Day is August 31, 2006.

SOURCE: University of Missouri Integrated Pest & Crop Management Newsletter, June 2, 2006.