By Clint Thompson
It is too early to say if this year’s whitefly impact on vegetables and cotton will rival 2017. But University of Georgia (UGA) Cooperative Extension vegetable entomologist Stormy Sparks insists the potential is there.
Sparks estimates that the whitefly population is about the same as a month ago. There have been some reports of populations existing primarily in kale. But there’s also low populations in winter crops that are still out there; namely cabbage and collards.
“The only reports I’ve had of anybody talking about any significant populations have been in kale,” Sparks said. “We haven’t heard of any populations in spring vegetables yet of any significance.”
Growers should have a better idea of this year’s whitefly effect next month once all the cotton has been planted and starts to grow.
“The potential is there. I was on the phone call (the other day) with everybody that does whitefly stuff. Everybody was talking about how it looks like 2017. The truth of the matter is the potential is there, but until you go through the weather conditions to see what happens with weather with management with those crops and management of those crops, you don’t really don’t know what happens,” Sparks said. “(UGA cotton entomologist) Phillip Roberts has for decades been telling me, if he sees whitefly populations in cotton in July, we’re in trouble. You’ll find whiteflies in cotton. But it’s really if you get into populations that are of concern in July, it’s going to be ugly.”
In 2017, whitefly populations showed up as early as May and June.
While colder temperatures do not eliminate whiteflies, they do kill many of their wild hosts. They also slow population development in cultivated hosts. Warmer temperatures this winter allowed for larger whitefly populations to overwinter and become mobile earlier.
Whiteflies cause feeding injury issues in vegetables and transmit two viruses: cucurbit leaf crumple virus and cucurbit yellow stunting disorder virus. Vegetables like squash, zucchini, cucumber, cantaloupe and snap beans are highly susceptible to these viruses. Commercial cultivars that have resistance or tolerance to these pathogens are not available.
Sparks and other specialists continue to preach sanitation with whitefly management. He said farmers have done better in recent years in getting rid of winter vegetables once they are done harvesting. That needs to continue with the spring crops once they are done.
“When you’re done with it, get rid of it. And that’s irrespective of what crop it is or the population level,” Sparks said.