Owners of pecan and persimmon trees in Northeast Mississippi have reason for frustration right about now. Many if not most such trees are host at this time of year to fall webworms.
The larvae of hyphantria cunea – often hatching 200 or more in a single egg cluster – create a silken sanctuary on these and other hardwoods, often stripping large expanses of leaves in the process. It’s something that happens every year, but this year they seem especially pronounced.
“The population is definitely higher than usual,” said Dr. Blake Layton, extension horticulturist with Mississippi State University.
Layton said commercial pecan growers are most affected by webworms. The loss of foliage can keep this year’s nuts from filling out well and can impact next year’s production as well. Most commercial growers, however, have access to high-pressure sprayers that can deliver effective insecticides high into trees.
Alarmed homeowners often resort to unorthodox controls, such as torches tied to long poles in an effort to burn the unsightly nests and their occupants – a method that Layton does not recommend.
“It’ll kill those that are in there, but it’ll also kill the bark on that part of the tree,” he said.
For nests that are within reach of a hose-end sprayer, Layton said homeowners can use any of several brands of spinosa-based insecticide – or the organic bacillus thuringiensis (Bt) – along with a tiny amount of surfactant to help penetrate the web. For small trees, for which defoliation can be a bigger threat, just opening low-hanging webs with a rake or other tool can control the worms by exposing them to predators.
“It is worth protecting smaller trees – anything under 12 to 15 feet,” Layton said.
ERROL CASTENS / Daily Journal Oxford Bureau