Unless more rain in the upcoming weeks can knock back populations, whiteflies are a huge concern for fall vegetable growers, according to Stormy Sparks, University of Georgia (UGA) Extension vegetable entomologist.
“Right now, it’s looking pretty bad. It could be devastating. The populations are really high, and we’re just now getting started,” Sparks said. “I’ve got squash where the adult counts are 200-plus per leaf. We’re just starting to see some virus. It’s pretty low, but that can increase rapidly.”
According to the most recent release of the US Drought Monitor, about half of Georgia’s counties are classified as ‘abnormally dry,’ including Tift County where Sparks is based at the UGA Tifton campus.
“They love hot, dry weather. I saw some cotton the other day. I haven’t seen cotton that looked that bad since I was in Rio Grande Valley of Texas,” Sparks said. “Those bad spots are very spotty right now, but if we stay hot and dry, it can get ugly in a hurry. It’s already ugly in some spots.”
Rainfall is needed to, not only help the crops grow, but knock back some of the whitefly populations.
Alabama Extension cotton entomologist Ron Smith said they’re finding whiteflies as far north as Quitman County (Georgia), which is just across from Eufala, Alabama. There’s also some in the Panhandle of Florida and in some fields in the corner of Alabama down in the extreme tip between Georgia and Florida. For more information about whiteflies’ impact in cotton, click here.
Whiteflies are especially dangerous since they 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. While this year’s whitefly infestation does not rival 2017 yet, the numbers are still bad and a concern for growers in the middle of planting this fall’s crop.
“We can battle the whitefly, it gets real ugly and real expensive but we can battle the whitefly in most crops. It’s those crops where we have virus problems where we don’t have resistance to that are the greatest concern,” Sparks said. “The yellow squash is extremely sensitive. Zucchini is tolerant but not really resistant. Cucumbers, you can produce a crop despite the virus. Tomatoes, we’ve got tomato yellow leaf curl, if you’re not growing a leaf curl resistant variety, you have the potential to losing the crop. But most people now are growing leaf curl resistant varieties in the fall.”
Lack of Cold Winter Temperatures
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.