TIPTONVILLE, Tenn. - How long should cotton growers expect a seed-applied insecticide to protect their seedlings from thrips damage? And when should they consider following a seed-applied insecticide with a foliar spray?
“In most cases, a seed-applied insecticide like Gaucho will provide about 28 days of thrips protection in our state,” says Scott Stewart, associate professor at the University of Tennessee’s Jackson Experiment Station. “By then, the crop should be in the third or fourth true leaf stage, maybe even the fifth or sixth leaf stage if you have warm weather and great emergence. That should be far enough along that any further thrips feeding shouldn’t affect crop earliness or yield.
“In most cases, it’s generally unnecessary to make an over-the-top spray if you’ve used a seed-applied insecticide. The exception would be if cool, wet weather weakens the seedlings and sets the plants back. In that case, you might want to make a foliar application of a product like Orthene at the first or second true leaf stage if you see a thrips problem developing in the field.”
Stewart adds that growers may find that an application of Orthene following a seed-applied insecticide can help enhance the protection normally experienced. But he cautions that growers who automatically apply Orthene at the same time they apply glyphoshate on Roundup Ready cotton may see little benefit if the application is made close to the fifth true leaf stage of growth.
John Lindamood, who produced 3,300 acres of cotton near Tiptonville, Tenn., last season, says he protects every acre he plants with Gaucho. But he says he will make an over-the-top application of Orthene if he sees thrips populations getting out of control.
“Last season, we did see a thrips problem where we unintentionally planted some untreated seed, and we went back in with Orthene to correct the situation,” he says. “But in most cases, Gaucho controls our thrips and aphids long enough for us to establish a healthy stand.”
Because Gaucho and Orthene complement one another in a thrips control program, growers who use both products can now earn extra savings through the Right Start program. This season, growers can qualify to earn a $2.00 rebate on each pound of Orthene they buy for every bag of cottonseed they purchase that is treated with Gaucho plus Kodiak biological fungicide. Right Start also assists growers in managing their risk by providing replant protection for registered participants. Growers may register for the program on line at www.gustafson.com/rightstart.
“Thrips are one of our worst insect pests in Tennessee cotton,” Stewart concludes. “It’s not uncommon to see as many as 30 thrips per plant on untreated seedlings, and I have seen as many as 100 per plant.
“I’d guess that growers in our state alone spend at least $5 million a year on thrips prevention, and thrips damage probably accounts for another $2 million in yield losses. It’s definitely a good idea to protect the crop before they reach the threshold level.”