Nematodes consolidating factor in early pest management
Every year, cotton growers in Texas and Oklahoma battle an unforeseen enemy—cotton nematodes. Unless you have a microscope, it is literally the invisible purveyor of death and destruction to cotton plants from the moment of seeding until the final boll eeks out what lint it will ultimately contribute to yield.
In the High Plains region of Texas and most of the Oklahoma growing regions, reniform and root-knot nematodes are the two most prevalent species. It’s an issue that’s easy to overlook, according to Jenny Dudak, assistant professor of plant and soil cciences at Oklahoma State University in Stillwater, Oklahoma.
“Nematode infestations can be detrimental to cotton production because they are the ‘silent pest’, she says. “Symptomology of infestations mimic other plant stressors and are often overlooked or mistaken for other issues, simply because they live underground.”
Growing awareness
Dudak and her Oklahoma colleagues are taking a more aggressive approach to identify nematodes across the cotton growing areas of the state and raise awareness among growers of the potential yield loss if left untreated.
“In Oklahoma, we have populations of both reniform and root-knot nematodes in our cotton production regions, while root-knot nematodes seem to be more prevalent,” she says. “The OSU Extension pathologist, Dr. Maira Duffeck, along with our Cotton IPM assistant specialist, Maxwell Smith, are currently collecting samples from cotton production regions in Oklahoma to verify the prevalence and identify which species are present and where they are in Oklahoma.”
According to Dudak, growers are generally aware of the issues with root-knot nematode, but reniform is a different story.
“Reniform nematodes are not constrained to sandy soils like root-knot nematodes are to survive,” she said. “They can thrive in soils with higher clay content. Historically, nematode infestations in Oklahoma have been synonymous with sandy soils, however now we also need to be considering the pest in our tighter soils.”
Out of sight, out of mind
Nematologists have been battling the “out of sight, out of mind” scenario for decades. Terry Wheeler, professor soilborne diseases of cotton and peanut, heads up one of the most prestigious research facilities across the Cotton Belt in Lubbock, Texas.
Her work with nematode resistant varieties has given growers added flexibility to manage the pest. “I prefer farmers to look at a fit for the nematode resistant varieties on their farms as the first option,” she said. “However, there is not always a good fit, especially if you are in a shorter maturing season due to location, or planting late, or because of your herbicide technology setup—such as dicamba versus Enlist.”
At this point, most nematode resistant varieties in the High Plains area are primarily bred for resistance or tolerance to the root-knot species though there are currently seven varieties with resistance against both root-knot and reniform nematodes.
With so much at stake, growers often consider boosting their nematode protection even if planting nematode resistant varieties. The upsides being more comprehensive nematode control along with other early season foliar pest control depending on the product.
“In terms of chemical options, the infurrow at-plant products generally offer better nematode control than the nematicide seed treatments, but of course they also take more time and effort from the producers to apply,” Wheeler said. “Velum (fluopyram) is the most commonly applied liquid infurrow product, and AgLogic 15GG (aldicarb) is the only granular infurrow product.”
Broader spectrum
While Velum is limited to nematicidal activity and disease suppression, AgLogic also protects against early season pests such as thrips and mites. “If rain is plentiful after planting, then both Velum and AgLogic have good control on root-knot nematode,” she said. “However, AgLogic does have an advantage in control if rain quantities are less, or if there is a delay of a week or so before receiving rain.”
Wheeler also works with Averland (abamectin)—a liquid infurrow-applied nematicide which also has activity against mites in cotton.
Nematodes aren’t the only issue concerning growers. The move away from broader spectrum pesticides in general has shifted the focus back to early season pests that were typically controlled by established materials such as AgLogic.
In Hockley County, Kerry Siders, Extension integrated pest management agent with Texas AgriLife Extension Service in Hockley and Cochran counties, (pictured above) said nematodes are just part of the problem.
“Terry Wheeler and I have worked with aldicarb for years in nematode trials, back when it was sold as Temik and now as AgLogic.
Beyond nematodes
“It’s still very effective,” he said. “And, and we’ve always known, other than just nematodes, you get thrips control. And then there’s always those other intangible benefits like the general health of a plant.”
Extension specialists in Oklahoma are voicing similar concerns about the threat of re-emerging early season pests in addition to nematodes.
“We have thrips every year of course,” said Maxwell Smith, assistant Extension specialist, entomology and plant pathology in Altus, Oklahoma. “That’s why growers were primarily using aldicarb (AgLogic). There’s some indication you can get some help with fleahoppers as well. We usually see a big run of fleahoppers—nearly every year.”
Future of acephate
With acephate currently under review by the Environmental Protection Agency, researchers and extension across the Cotton Belt are concerned about the product’s future.
While acephate is still widely used for thrips and fleahoppers, the possibility of losing the product along with the growing awareness of nematode issues in Oklahoma cotton growing areas are regenerating interest in AgLogic.
“As we discover more and more nematode issues, I think it gives us another tool in the toolbox to combat those issues as well as deal with some of our other early season problems,” Smith said.
