Eastern Tent Caterpillar Diagnostic Guide
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.
Trees at Risk
Common hosts of the Eastern tent caterpillar 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).
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 in the crotch of branches.
- Eastern tent caterpillar can be distinguished easily from its black color with a white stripe down the back.
- Lines of blue spots run longitudinally between yellow lines down the sides of the caterpillars.
- Eggs hatch in the spring at about the same time as leaf emergence on cherry.
- Young larvae begin building their silken tents in a major branch fork or crotch.
- The larvae feed for a period of six to eight weeks before migrating to a protected site to pupate.
- The pupal stage lasts for about three weeks.
- Adult moths emerge in early summer. Females deposit their egg masses around small twigs where they over winter.
- One generation per year.
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. The Eastern tent caterpillar is easy to control if treatment applications are timed correctly in the spring of the year.
Other Treatment Practices
- Prune out the nests after they have formed. Early morning or late afternoon is a good time to do this as most of the caterpillars will be in the nest.
- Promote health and vigor with proper irrigation, mulching, proper pruning and prescription based fertilization practices.
- Use Lepitect Infusible on trees that cannot be sprayed or treated with soil applications.
A high level of control can be expected if treatment applications are timed correctly. Lepitect™ will be absorbed and translocated as the trees begin to develop their leaves and transpire, therefore Lepitect will be effective on later instars due to lack of transpiration at egg hatch and early instar development.
Conserve™ has a short residual (4-7 days) but is softer on beneficial insects, whereas Up Star Gold™ will provide slightly longer residual (7-14 days), but is broad spectrum.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org