Released June 15, 2007
LITTLE ROCK, Ark. - Arkansas cotton farmers are fighting one of the most severe outbreaks of thrips – a yield-robbing insect – that they've seen in many years, according to Gus Lorenz, entomologist with the University of Arkansas Cooperative Extension Service.
He said farmers are overwhelmed by the insects, leading many to question if their seed treatments are in-furrow treatment of insecticides are working.
"As bad as it may look," he said, "it's working better than you think. Our untreated checks in our trials indicate it could be a lot worse."
Because of the overwhelming numbers of thrips, the usual 80 percent to 90 percent control with insecticides isn't enough. Lorenz said the situation is so bad that many farmers need to apply foliar insecticides if they're to gain the upper hand.
Products of choice are bidrin, dimethoate and acephate, Lorenz said. The first two are much less disruptive to beneficial insects, which will help avoid secondary pest problems such as aphids.
"Despite their small size – one-twelfth of an inch – these insects have the potential to cause yield reductions of more than 100 pounds of lint per acre," he said. Damage includes leaf distortion, stunted plants, delays in maturity, reduced yield potential up to 500 pounds an acre and, in severe cases, stand loss.
Lorenz recommends preventative treatment at planting. He said foliar insecticide sprays are recommended if there are two to three thrips per plant.
Farmers are also seeing aphids and mites in seedling cotton. Lorenz said a field in Poinsett County and several fields in nearby Mississippi are being treated for mites.
"Early detection and control can mean the difference in achieving control and reducing costs," Lorenz said. "As the weather begins to turn hot and dry, you can expect mite activity to pick up."
Lorenz said the extension service is also finding plant bugs in seedling cotton plots. He said a symptom of their damage is finding a dead leaf in the terminal.
Rob Hogan, extension economist at the Northeast Research and Extension Center in Keiser (Mississippi County), said it's important not to get behind on insect control no matter how bad it hurts.
"This year, it will be difficult enough to pencil a break-even or profitable season given high fertilizer and fuel prices without other troubling issues," he said.
Hogan said there's not a great deal of price difference between insecticide application alternatives for thrips control. Producers can choose the treatment choice that best fits their operations, he said.
"Nonetheless, there are some differences, and this year cost control is going to be of paramount importance; producers need to save every cent that can be saved on a per acre basis without giving up yield or gross revenue," Hogan said.
In some years, extension has received a few calls about poor insect control after insecticide applications.
"Typically, the culprit has been poor application," Lorenz said. "Just remember, coverage is everything with control of thrips."
Saving an application cost by tank mixing an insecticide and herbicide may not be a savings if control is poor, Lorenz said. "In the long run, it may be a better economic decision to make two applications, use correct spray tips for each and get effective control on each application," he said.
One practice that nearly always has hidden costs is the practice of adding an insecticide to a required herbicide application, Hogan said. The only cost effective time to spray for insects is when pest counts meet and/or exceed extension recommended thresholds.
For more information on cotton production, contact your county extension agent or visit http://www.uaex.edu/ and select Agriculture, then Cotton. The Cooperative Extension Service is part of the U of A Division of Agriculture.
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http://www.uaex.edu/news/june2007/0615thrips.htm
Contact: Lamar James, (501) 671-2187 or (501) 753-0207, ljames@uaex.edu
