It looks like thick spiderwebs in trees with defoliated branches and Tom Springstun, Scott County Purdue Extension Educator said that area residents have been calling his office about the fall webworms.
These white to tan fuzzy caterpillars have black dots on their back and can be up to an inch and a half long. When unchecked by the wide variety of insects and birds that feed on them, caterpillars can defoliate entire trees in late summer.
“Although this late season defoliation is too close to the time of leaf drop to harm plant health, most homeowners prefer to keep unsightly webs off their trees,” said Springstun.
Control of fall webworm caterpillars is best achieved if actions are taken before the tree is covered with webs. Small webs can be simply pruned off, or raked off with your hand, and destroyed if only a small proportion of the tree is affected, and they are within easy reach, he said. “Streams of high pressure from a water hose may also be effective in getting the webs out of trees,” he said.
“Pesticides should only be used when the extent of the webbing or number of webs is too large to make pruning practical,” Springstun said. Applications of the biobased insecticides acelepryn and Bacillus thuringiensis, which conserve the webworm’s insect natural enemies, are especially effective when applied early in the infestation process.
“The fall webworms and their resulting silky webs covering them will not kill your trees, but the webs will likely remain in the trees through the winter if they are not removed,” he said.
For a free download of the Purdue Extension Publication on Fall Webworm, E-225-W, go to the Purdue Media Distribution Center at https://extension.entm.purdue.edu/publications/E-255.pdf
For more info on this or other Yard or Garden topics, contact Springstun at tsprings@purdue.edu, or call him at (812) 752-8450.
