Louisiana Cotton: Western Flower Thrips Pressure – Control Options Weighed
Heavy populations of western flower thrips (WFT) have been mixed into general thrips infestations in Louisiana cotton this season. Entomologists have been running a series of evaluations of both older, established products and Radiant.
We talked late Tuesday afternoon about thrips control options with David Kerns, Associate Professor of Entomology at the Macon Ridge REC, and Sebe Brown, the state’s Northeast Region Extension Entomologist.
Based on plot evaluations, they said:
Radiant provided about 90% control 4 days after treatment (DAT). “In our tests we did not see any appreciable difference between the 1.5 ounce/acre rate and the 3-ounce rate,” said Kerns.
“A 1.5-ounce rate of Radian runs $8 an acre, which is hard for many producers to swallow,” said Brown. “A lot of them want to use Bidrin or Dimethoate, but with high numbers of WFT, we don’t think it’s giving as much control as might be needed, especially Dimethoate.”
Kerns said that results with Dimethoate were “disappointing.”
“A lot of these are WFT, half or more of the populations, and we’re not picking up enough of them,” Kerns added. “We looked at both the 4 ounce/acre standard shot and then doubled the rate to 8 ounces, and neither looked that good.”
Control with Radiant was 90% 4 DAT, Kerns said. Additionally, Kerns noted, Radiant should be applied with “a good non-ionic surfactant or MSO.”
Acephate at a half-pound/acre rate also is giving about 90% control 4 DAT, he said.
“Bidrin doesn’t deliver quite as much control, but with the first shot it’s usually sufficient where cotton is just coming out of the ground and plants don’t have a lot of colony development,” Kerns added.
In the Radiant plots there appeared to be more very small immatures present in the samples, Kerns said, “which may indicate that that product may be breaking a little sooner than a half-pound of acephate.”
Radiant, though, is softer on beneficials, they both pointed out.
“We’re already picking up spider mites, plus aphids are out there, too,” Brown reported. “If we go with acephate, that could blow up spider mites.”
None of the products will deliver better than 95% control, so that will leave some lingering numbers. And based on thrips populations being found on a wide basis, more will find their way into fields after treatments. WFT also feed on spider mite eggs, so the presence of a few WFT can help suppress mite populations, they pointed out