Native to North America, the eastern tent caterpillar, Malacosoma americanum, is a defoliating caterpillar that has been reported as early as 1646. Up until the 1970’s and 1980’s the eastern tent caterpillar had been considered one of the most common and destructive defoliating insects in the eastern United States. In late spring and early summer, the eastern tent caterpillar creates an unsightly nest or tent in the crotch of branches. The feeding of the larvae in late spring and early summer strips the foliage from trees. Complete defoliation can occur when caterpillar populations are high. The larvae can become messy as they crawl on sidewalks, patios, and driveways where they become squashed.
Feeding from Eastern tent caterpillar larvae in late spring and early summer can completely defoliate foliage from trees. Healthy trees can tolerate a single defoliation event, however, multiple defoliation events can cause dieback and when combined with abiotic stress events can be detrimental to the tree. The Eastern tent caterpillar is easy to control if treatment applications are timed correctly in the spring of the year; however, early infestations of the pest are also easily controlled with pruning out/removing nests by hand and squishing.
Other Treatment Practices
- In early spring small nests can be removed and destroyed by hand, larger nests can be pruned out and destroyed. Early morning or late afternoon is a good time to do this as most of the caterpillars will be in the nest.
- Natural predators such as birds and parasitic wasps can also help control this pest.
- Promote health and vigor with proper irrigation, mulching, proper pruning and prescription based fertilization practices.
A high level of control can be expected if treatment applications are timed correctly. Lepitect will only work on later instars due to lack of transpiration at egg hatch and early instar development. Mectinite will provide good season long control.
Signs of Damage
- Stripping of the foliage in late spring and early summer
- Mature caterpillars are usually black with a white stripe down the back
- A line of blue spots run between yellow lines down the sides of the caterpillars
- Adult moths are reddish brown with two whitish stripes running across each forewing
- A silky nest or tent that doesn’t encompass foliage in the crotch of branches
- Egg masses are covered with a shiny, black varnish-like material that encircles branches that are about a pencil-size or smaller in diameter
Photo: Patrick Anderson
Photo: G. Keith Douce
University of Georgia, Bugwood.org
Photo: Joseph O’Brien
USDA Forest Service, Bugwood.org
Photo: Lacy L. Hyche
Auburn University, Bugwood.org
Trees At Risk
Common hosts include Prunus species such as cherry, plum, and peach, as well as flowering crabapple (Malus), hawthorn (Craetagus), and pear (Pyrus). Other hosts include maple (Acer), ash (Fraxinus), birch (Betula), oak (Quercus), willow (Salix), and poplar (Populus).
- The caterpillars overwinter as an egg, within a mass of 150-400 eggs.
- Eggs hatch in the spring at about the same time as leaf emergence on cherry.
- Young larvae begin building their communal nests via silken tents in a major branch fork or crotch.
- The larvae feed for a period of four to six weeks (beginning at 51-190 GDD) before migrating to a protected site to pupate.
- The pupal stage lasts for about three weeks.
- Adult moths emerge in early summer. (Flight stages are late May – June).
- Females deposit their egg masses around small twigs where they over winter.
- One generation per year.
National Phenology Network
University of Kentucky
Ohio State University
Johnson, W.T., Lyon, H.H. 1991. Insects That Feed On Trees and Shrubs.
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.