Photo by Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org
Southeast citrus growers hoping that the Feb. 1 freeze would wipe out the Asian citrus psyllid (ACP) population are going to be disappointed.
“What we do know about freezes is a lot of time they will reduce or delay the buildup of many of the populations of pests that we worry about,” said Lauren Diepenbrock, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) assistant professor and entomologist. She cited 2008 research conducted by UF/IFAS Citrus Research and Education Center director Michael Rogers.
“You still have about 20% to 80% of psyllids that survive a freeze of 10 hours below freezing,” Diepenbrock said. “The freeze probably didn’t kill all of the psyllids. That’s unfortunate, but the population is likely reduced. If young flush or buds are depleted, then they’ve lost a preferred food resource. It’ll take a little while for them to come back.”
ACP management is crucial since the insect vectors citrus greening disease, which has devastated Florida’s citrus crop and is a potential threat to the crop in the cold-hardy citrus region of North Florida and South Georgia.
Diepenbrock was part of a post-freeze recovery seminar hosted by the UF/IFAS Citrus Team on Feb. 11. She talked about various insects but focused on the ACP.
She said Rogers’ 2008 research looked at what happened to psyllids based on whether they were in the exterior or interior of a tree. The study showed that psyllids can survive freezing temperatures.
“With no freeze protection, you have about 70% ACP mortality. With freeze protection, you get a little over 50% mortality,” Diepenbrock said. “The research looked at the insides and outsides of the canopies; basically, inside toward the center of the tree and outside where the flush would have been. You have between 54% and 68% mortality, so there’s still a decent amount of survival.”
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