When the most common sign is yield loss, it makes it difficult to put a finger on the cause. In a field of cotton or corn, the culprit is likely underground pests: nematodes.
Kathy Lawrence, a professor and researcher in the Auburn University department of entomology and plant pathology, said Alabama’s major nematodes are the root knot nematode and the reniform nematode in cotton, as well as the stubby root nematode in corn.
“The root knot nematode is our Southern cotton nematode and that’s one of our main ones,” Lawrence said. “It does like all the sandy soil. I find it most often in the southern part of the state.”
She said the reniform nematode is more of a silty soil type of nematode. This one is most often in north Alabama, but there is a place in the southern area of the state near Atmore where there’s a hotspot of those nematodes. During cool, wet springs—especially in early-planted corn—the stubby-root nematode will show up.
Lawrence said the symptoms of a nematode problem are not easy to tell apart above ground.
“Below ground, the root knot nematode will leave some galls, but the reniform will not,” she said. “Truly the best symptom we have is yield loss, although it is not exactly a visual producers can identify and correct because it appears too late.”
Symptoms are nondescript—stunted, unhealthy-looking plants. The only way to know which nematode is causing problems is to conduct a soil test and have it analyzed in the lab. When the results are in, producers can implement control measures.
“The best thing producers could ever do to avoid nematode problems is crop rotation,” Lawrence said. “Our reniform nematode does not go to corn or peanuts. There are also resistant soybeans. If producers can rotate to any of those others, that helps curb nematode presence tremendously.”
The root knot nematode does go to a lot of other crops, but the southern root knot that attacks cotton does not attack peanut. Lawrence said that’s an ideal rotation.
Alabama Cooperative Extension contributed this article.