Insecticide Rotation Key in Long-Term Management of Whiteflies

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By Clint Thompson

Insecticide rotation when managing whiteflies remains key to long-term success in the Southeast. It has to be if growers want to avoid insecticide resistance developing.

Whiteflies infest fall cucurbits.

Stormy Sparks, University of Georgia (UGA) Cooperative Extension vegetable entomologist, believes farmers have improved in recent years in protecting their insecticides for the future.

“The same chemistries that we rely on, primarily the group 28s, the diamides, and then the group 4s, the neonicotinoids; there’s several others that we can use, but those are our main ones. Probably the good news is that we still have those,” Sparks said.

“There’s always some indications out there of potential resistance. But I think growers are doing a good job of rotating and using as many chemistries as they can. The fact that we still have them available is a good indication that growers are doing a good job of rotating chemistries and maintaining efficacy as best they can.”

Whitefly Impact

Whiteflies attack various crops, including watermelon, cabbage, zucchini and snap beans. They overwinter in Georgia on vegetable crops, like cabbage, collard greens and kale. Just as significant, though, is that whiteflies can also transmit cucurbit leaf crumple virus and cucurbit yellow stunting disorder virus. According to UGA crop loss estimates for fall 2017, these viruses caused between 30% and 50% of crop loss in squash and cucumbers and nearly 80% of crop loss in snap beans.

It is important that growers continue to preserve the insecticides they have. There are not any new chemistries coming available anytime soon.

“If we got resistance to either of those two groups, if you get resistance to one and shift your primary reliance to the other, that one’s not going to last long,” Sparks added. “That’s one of our big issues every year, one of our big emphases, is monitoring what’s going on out there and making sure we maintain the chemistries we have. It’s getting more and more difficult to get new chemistries, particularly in the insecticide world.

“One of the things I think growers across agriculture have done a much better job of the last few years is managing whiteflies in multiple crops. Whiteflies are not just a vegetable issue. They’re not just a cotton issue. They go from one system to the next. Management in one system affects the potential management in the next. I think our growers have done a much better job of that the past couple of years and avoiding the problem becoming much more severe than it has been.”