Thrips Gone Wild

01/01/2010 02:00:00 AM
Vicky Boyd, Editor

“If you’re up in Quincy, it’s a whole different scenario than in southeast or southwest Florida,” Charlie Mellinger says. “If you’re dealing with Western flower thrips with tomato spotted wilt virus present, then the threshold is much lower because you can’t tolerate a few thrips.

“But if you’re in south Florida or even on the East Coast where we don’t have much TSWV, the Western flower thrips threshold can be much higher than in Georgia or north Florida.”

If Western flower thrips exceed the threshold, carefully choose an insecticide that will preserve the beneficials, Funderburk says.

Fenpropathrin (Danitol) and pyrethroids kill the predators as well as the native thrips, leaving Western flower thrips alone to go wild.

Learning about new products

The spinosyns have been the main products of choice because they are effective against Western flower thrips yet soft on minute pirate bugs, Weiss says.

Registration of a handful of soft insecticides that are effective against thrips is on the horizon, Funderburk says.

Although the new products should relieve some of the resistance pressure, they could cause resistance problems if not used carefully, he says. When they’re registered, the newcomers should not be viewed as stand-alone controls and should be incorporated into an IPM program.

Researchers also are learning how to use already registered products more effectively against Western flower thrips.

For example, Requiem, a biological insecticide derived from a plant extract by Davis, Calif.-based AgraQuest, is relatively ineffective against thrips when applied just once, Funderburk says. But follow the initial application five to seven days later with another application of Requiem, and thrips control improves significantly.

Going vertical to fight Western flower thrips

Below are highlights of the integrated pest management plan for Western flower thrips in peppers and eggplant developed by Joe Funderburk, a University of Florida professor of entomology and nematology, and a group of colleagues.

In scouting programs, distinguish between adult and larval thrips, and identify adult thrips to species.

Economic thresholds: about 6 adult western flower thrips and melon thrips per flower, and about 2 thrips larvae per fruit.

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