Eastern Tent Caterpillar
Malacosoma americanum Fabricius


Hanson, T., and E. B. Walker. [n.d.] Field guide to common insect pests of urban trees in the Northeast. Waterbury, VT: Department of Forests, Parks and Recreation. http://www.state.vt.us/anr/fpr/forestry/pubs/pest.html


Lepidoptera: Lasiocampidae

Hosts: Primarily ornamental cherry, wild cherry, and apple, but also other shade, forest, and fruit trees

Evidence: Spindle-shaped egg masses which encircle twigs and are covered with hardened varnish-like material can be seen from late summer until early spring. In spring, look for silken tents in crotches of trees (a). Caterpillars are furry and bluish with black heads and a white stripe down the back (b,c). Defoliation is usually complete by mid-June. When damage is severe, only larger veins and leaf petioles remain. The chunky, chocolate brown moths have narrow white bands on their wings and are attracted to light.

c. Eastern tent caterpillar has a white stripe down the back, while forest tent caterpillar has keyhole-shaped white spots.

Life Cycle: Winter is spent in masses of 100-300 eggs. Hatching occurs in early spring, and the newly-emerged, gregarious larvae construct tents. They leave the nest on warm sunny days to feed on nearby foliage. When full grown, larvae wander in search of pupation sites. Pupation takes place in silken, yellow-dusted cocoons on trees and other vegetation, and on fences, buildings, and other structures. Adults emerge in July.

Management: Reduced growth and branch damage may result from heavy or repeated defoliation. Natural enemies such as birds, parasites, and pathogens and adverse weather conditions often control the eastern tent caterpillar effectively. From July until early spring, twigs containing egg masses can be pruned off and destroyed. Mechanical removal and destruction of tents as they appear in early spring is a control option. Bacillus thuringiensis and various chemical insecticides can be used to control larvae.

Similar Species: The forest tent caterpillar (M-2) and gypsy moth (O-1) contruct no tent but their caterpillars may associate with the eastern tent caterpillars and larvae of all three may occur within a single tent. Other tent-making species such as the fall webworm and uglynest caterpillar occur later in the season (July and August).

Photo Credits:

Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.

References:

Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 202-203;

Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs . 2nd edition. Cornell University Press. p 168-169;

Rose, A.H. and Lindquist, O.H. 1982. Insects of Eastern Hardwood Trees. Canadian Forest Service Publication, Forestry Technical Report 29. p 245.

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