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Keep an Eye on Thrips

06-14CFcvr Thrips are tiny, but mighty, insects that have the ability to delay maturity and damage cotton in the very early stages of growth, and, if not controlled properly, reduce lint yield at harvest.

Gus Lorenz, University of Arkansas entomologist, says, “We rank thrips as the No. 2 pest right behind plant bugs. If you look at dollars spent and damage caused, they come out as the second most important pest in cotton production in Arkansas.”

Conventional tillage can increase thrips numbers, and thrips typically are a problem until cotton reaches the third or fourth leaf stage. Anything that holds the crop at that stage for a longer period of time, such as cool weather or preemergent herbicides, will increase the severity of damage.

“For the most part, our producers have moved to seed treatments for thrips control,” says Angus Catchot, Mississippi State University entomologist. “These types of products include thiamethoxam – Cruiser, Avicta Duo and Acceleron N; or imidacloprid – Gaucho, Aeris and Acceleron FI.”

Lorenz notes that Arkansas farmers also adopted the use of seed treatments very quickly. “Seed treatments are a big part of our standard regimen for thrips control in cotton,” he says. “They may not be quite as good as infurrow Temik, but they are good enough, plus the convenience and safety factors come into play. Today, 95 percent of our cotton is treated.”

Increased Tolerance Showing Up

Although insecticide seed treatments have become widely adopted by producers, both Catchot and Lorenz note that in the past couple of years, they have seen more damage than they would have expected behind the thiamethoxam- based seed treatments. “Currently in the Mid-South, it appears that there may be some increased tolerance with thrips to that particular active,” Catchot says. “We are working very closely with the registrants and others to figure out exactly what we are dealing with.”

The Mississippi entomologist says if a producer did plant cotton with a thiamethoxam- based seed treatment, make a foliar application for thrips control when the plant comes out of the ground and follow up with good scouting to determine if additional sprays are needed. “The additional foliar sprays for thrips may or may not be necessary,” he adds. “We are also watching the imidacloprid-based products very carefully, given that it is in the same class of chemistry.”

Yield Impact

Even though plants generally recover from thrips early on, research trials have shown, in some instances, 200 to 300 pounds difference in lint between control and no control, which means that thrips can definitely reduce yield, depending on the year. “With this in mind,” Catchot says, “itÊs important to scout carefully this season and take the necessary measures to control thrips in cotton.”

Contact Carroll Smith at (901) 326-4443 or csmith@onegrower.com.