This is the kind of year nematodes appreciate. The soil is hot, and farmers' crops are stressed. It's ideal for the tiny, soilborne organisms which thrive on plant roots.
“The reality is that nematodes are showing up in a lot of cotton fields this year,” said Terry Kirkpatrick, professor and nematode expert for the University of Arkansas Cooperative Extension Service.
He is director of the Arkansas Nematode Diagnostic Laboratory at the UA Southwest Research and Extension Center at Hope, Ark.
Nematode damage to plant roots leads to a range of problems, including poor plant growth, poor fruit, seed, or fiber production, or plant death.
Many nematode problems each year are mistakenly attributed to poor fertility, insect problems or weather.
Because they damage the root system of the plants, nematodes are piling on to problems in cotton caused by an already harsh environment of dry soil and extreme heat, Kirkpatrick said.
“Visible problems tend to show up more in center-pivot irrigation fields than furrow-irrigated fields,” he noted. “The reason is that it's impossible to put as much water on a field with a center-pivot as with furrow irrigation.”
If the nematode problem is bad in irrigated fields, it's an epidemic in many non-irrigated fields, according to Kirkpatrick.
“These fields are infested, and the plants show it,” he said. “The problem is that nematodes may be the least of the worries for farmers with dryland fields. Many of these fields are in bad shape because of the weather.”
Meanwhile, cyst nematodes and root-knot nematodes are damaging soybeans from the Missouri border to the Louisiana border.
“These are early-maturing varieties that were planted on light-textured soil where root-knot nematodes were present. They've taken their toll on those plants.”
Kirkpatrick estimated that 10 percent of the Arkansas' soybean acreage is infested with root-knot nematodes, and “certainly, a greater acreage is infested with cyst nematodes.”
He said the corn crop isn't suffering much from nematodes, but there's another problem brewing.
Root-knot nematodes don't damage corn much, especially if it's irrigated, he said. But the nematode population explodes in the crop. If growers plant susceptible cotton or soybeans next year, they need to be aware that they've probably built a sizeable root-knot nematode problem in the soil with the corn crop.
The good news is that reniform nematode populations in corn are way down. “If you typically have a problem with this nematode, you've done yourself a lot of good this year by growing corn,” Kirkpatrick said.
He recommended that as growers go about their normal duties, they make notes on weak spots in fields and draw maps. Ideally, they should have cotton scouts carry handheld GPS and mark the spots for later sampling.
Get serious about sampling cotton, soybean and corn crops at the end of the year. The best thing for growers is to spend some time this fall taking nematode samples. This way, there is no doubt where the nematode problems are and which nematodes are involved.
There's a small cost-recovery fee charged for nematode assays. If samples are taken to a county agent, the samples will, however, be shipped to the laboratory at no charge.
For more information on nematodes or sampling, growers can call their agents or visit www.uaex.edu. Select Agriculture, Cotton and Nematodes.