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“The best way to manage nematodes is to be as proactive as possible,” says Tom Allen, associate professor with an Extension and research appointment at the Delta Research and Extension Center at Stoneville. “And the first step in doing that is to sample, sample, sample, sample — I can’t emphasize this enough."
SOIL SAMPLING is a critical first step in managing nematodes in cotton. "If you have a nematode problem in your cotton fields, you could easily be losing the cost of the soil sample in yield," says Tom Allen.
Rotation is best strategy
There are, Allen says, very few commercially available cotton varieties with some level of nematode resistance, “and even that is going to be more toward the level of tolerance — for root-knot nematodes only. At present commercially available varieties with tolerance to reniform nematodes are not available.
“One of your best nematode management strategies is to plant a rotational crop, depending on nematode species present. Grain sorghum is a good alternative, because root-knot nematodes also go to corn and soybeans. Grain sorghum is also a good alternative for reniform nematodes. But, if you have reniform nematodes present, corn is a good alternative.
“If you have root-knot nematodes in corn, you may not see a substantial yield drag, or if you pull up a corn plant, you may not observe galls indicative of a root-knot problem. But corn will increase root-knot nematode populations. Your best bet is to stick a probe in the ground and send a sample to a lab for analysis.”
Aside from that, Allen says, “You can try and find a cotton variety with some tolerance, but some of the varieties may be so new there won’t be a tremendous amount of information available.”
A number of growers have asked about seed-applied nematicides, he says. “I don’t know of many researchers who have a good data set on this. But with the nematode numbers that we’re consistently seeing in some Mississippi cotton fields, seed-applied nematicides are not doing the job growers are expecting them to do.
“Fumigants are another potential management strategy, but they have their fit in specific areas. Where you know you have a nematode problem, based on field maps, yield maps, soil classification types, general poor performance, etc., your best bet is going to be site-specific management. You don’t want to spend $50 per acre across a 3,000-acre farm treating with a fumigant for something that may be a problem on only 5 to 15 acres.