By Clint Thompson
Whitefly management in the Southeast is not predicated on thresholds; how many whiteflies can a vegetable plant tolerate before insecticides need to be applied.
Growers know they will encounter the insect pest, so thresholds won’t matter. Management involves more preventative measures, says Stormy Sparks, University of Georgia Cooperative Extension vegetable entomologist.
Sparks was part of a panel discussion on whiteflies during the recent Citrus & Specialty Crop Expo in Tampa, Florida.
“If you go look at literature and look at like cotton, where a lot of work has been done with whiteflies and thresholds, it’s like five per leaf; third leaf down from the terminal. You can use that in any crop in South Georgia,” Sparks said. “You’re not going to find one or two per leaf, in most cases. If you do, come back in three days and you’ll have five per leaf. In most areas, in Tift County and Colquitt County, it’s preventative. There’s no threshold because you know you’re going to have them. There’s no doubt about it. That’s where we’re at with whiteflies.”
Hugh Smith, an associate professor of entomology and nematology at the UF/IFAS Gulf Coast Research and Education Center, was part of the same panel discussion and highlighted thresholds in Florida.
“I don’t think the concepts of thresholds is very useful, particularly in Florida. Particularly with whiteflies, our concern is virus. With cucurbits and tomatoes, we’re really concerned with virus. We know the virus is going to show up in the state of Florida,” Smith said. “I don’t think growers, at least in this context, are using thresholds, it’s more about being proactive with virus.”
Whitefly infestations are significant because of their potential impact throughout the year. They typically migrate from winter vegetables to spring vegetables to agronomic crops, like cotton, to fall vegetables and back to winter vegetables. The buildup of whiteflies is concerning since their feeding injuries in vegetables can lead to virus transmission, including cucurbit leaf crumple virus, cucurbit yellow stunting disorder virus, cucurbit chlorotic yellow virus, squash vein yellowing virus and tomato yellow leaf curl virus.