- Branches with browned leaves
- Leaves tied together with webs
- Striped green caterpillar in webs
Leaves on ends of branches become webbed together and turn brown as lime-green caterpillars skeletonize leaf tissue. Heavily infested trees appear frosted brown. Late-stage caterpillars drop to the ground from the trees on silken strands to search for a sheltered place to make their white, silk-covered cocoons. The dangling caterpillars can be a nuisance under heavily infested trees. Masses of these white cocoons superfically resemble puffed rice and can be found in bark crevices as well as glued onto structures under shingles, windows, and door frames from October through May.
Mimosa webworms winter in cocoons in sheltered areas. In early June, adults emerge and lay eggs on trees. First webs can be seen on ends of branches in mid-June when oak leaf hydrangea and tree lilac are in bloom. Larvae take three weeks to turn into pupae. The second generation of adults fly and lay eggs starting in late July. Caterpillars are out in early August and start dropping from trees to pupate at the end of the month. A third generation occurs in the fall.
To kill caterpillars without creating other pest problems (spider mites, scale insects) it is best to use biorational pesticides (spinosad, Bacillus thuringensis, chlorantraniliprole). Caterpillars may have to feed on treated leaves for 1-2 days to get a lethal dose of these materials. When pests are discovered late in season and extensive damage is present, it may be necessary to spray a rescue material to kill caterpillars quickly. Rescue treatments include Sevin(carbaryl) or a pyrethroid (eg. bifenthrin, cyfluthrin, deltamethrin,permethrin). To protect bees avoid applying insecticides when trees are flowering.
Active Ingredients include: Bacillus thuringiensis var. Kurstaki, Bifenthrin, Carbaryl, Chlorantraniliprole, Cyfluthrin, Indoxacarb, Lambda- cyhalothrin, Permethrin, Spinosad, Tebufenozide
