This week the Caribou-Targhee National Forest released information about two native tent caterpillars that are becoming active on the forest and adjacent lands.
According to information provided by the Forest Service, the western tent caterpillar makes “silken tents in the branches of shrubs and trees.”
“Caterpillars live and feed together on the foliage using the tent as protection just before they go off on their own to find a place to pupate in the process of becoming a moth,” said Lynn Ballard of the Caribou-Targhee National Forest. Their preferred foods are serviceberry, chokecherry, alder, bitterbrush, willow, snowberry, maple, fruit trees and aspen. In 2014, the defoliation caused by these caterpillars is wide spread.”
According to information provided by the Forest Service, forest tent caterpillars are often “seen crawling up and down the main tree trunk during the day searching for tree foliage to eat or shelter.”
“Forest tent caterpillars feed primarily on aspen, but can be found on maples, alder, and a wide range of other deciduous plants during June,” said Ballard.
According to information provided by the Forest Service, in early July both species of the caterpillars pupate in white to yellowish silken cocoons. Adult moths usually emerge in early August.
“Eggs are laid in masses of 100-350 on live branches of their favorite plants to eat, and can completely encircle small diameter twigs,” said Ballard. “Caterpillars hatch in the fall, but remain in the egg mass until the following spring. Outbreaks of these caterpillars can be widespread with hundreds to thousands of acres defoliated.”
According to Ballard, if defoliation happens early in the season, some deciduous plants will put out a second flush of leaves.
“Fortunately, outbreaks are short lived and subside after a year or two,” he said. “Parasitic wasps and flies, or a polyhedral virus often are the primary factors that control an outbreak.”
According to information provided by the Forest Service, caterpillar damage to trees, shrubs and other plants can “be reduced by killing or removing caterpillars and egg masses.”
“Several chemical insecticides and a microbial insecticide are available for treating individual trees or small groups of trees,” Ballard said. “These insecticide treatments are most effective when caterpillars are small and have just begun to feed, typically in late spring or early summer before damage occurs.”
According to information provided by the Forest Service, removing tents that have western tent caterpillars inside can reduce defoliation on specific plants.
For the forest tent caterpillar, barriers can be applied to the “trunk of individual trees to prevent migrations into the canopy from the ground.”
“For both species, crushing egg masses in the fall and early spring may provide some protection to ornamental plants,” said Ballard.
Private landowners wishing to treat individual trees for tent caterpillar infestations can contact Lincoln County Weed and Pest at 885-9333.