The eastern tent caterpillar, Malacosoma americanum, is a pest native to North America that can cause serious defoliation to deciduous trees in the family Rosaceae, in particular to Cherry (Prunus) and Apple (Malus).It is often mistaken for the Gypsy moth caterpillar as they emerge at similar times in the spring, and the fall webworm (which appears in late summer and fall). Eastern tent caterpillars can defoliate a tree but trees will usually recover from one or two years of damage. Successive years of high populations can cause stunted growth for host plants and may make them susceptible to disease.
The adult moth will lay 150-300 eggs that will overwinter in shiny, varnished-looking, black masses encircling a branch or limb. Eastern tent caterpillar egg masses do not encompass foliage as the fall webworm masses do. The egg masses are easily spotted especially during the winter months when trees are bare of foliage.
Whitney Cranshaw, Colorado State University, Bugwood.org
It is in March when the eggs hatch that their presence is easily seen. As the young hatch they spin their silken tent in the crotch of a branch. The newly emerged caterpillars will stay together, sometimes joining with the young from a nearby egg mass to form one large community.
The caterpillars will emerge from their protective tent in the early morning, in the evening or even at night to feed. They will stay within their enclosure during the heat of the day, if it is raining or if it is too cold. Over the next 4-6 weeks they will feed on nearby foliage, increasing the size of the tent to accommodate their increasing size. The black caterpillar with a white stripe bordered by blue down its back will reach a length of 2 to 2 ½” at which point they will stop feeding and will leave the tent.
The larvae are frequently seen wandering across walkways, roads, buildings, and other plants as they look for protected places to spin a 1” long, whitish cocoon and pupate The reddish-brown adult moth will emerge 3 weeks later to mate and lay the eggs on small branches that will hatch the following spring. There is one generation per year and populations will fluctuate from year to year.
The Eastern tent caterpillar favors members of the Rosaceae family as its host plants. This family includes the genus Prunus which encompasses almond, apricot, cherry, crabapple, peach, plum, and quince, the genus Cotoneaster which includes hawthorn and rowans, and the genus Sorbus which contains service tree and mountain-ash.
Despite good cultural practices, pests and diseases at times may appear. Chemical control should be used only after all other methods have failed. READ THE LABEL on each pesticide container before each use. Apply as directed. Heed all warnings and precautions. Store pesticides in their original labeled containers out of reach of children, irresponsible people and pets, preferable under lock and key. Dispose of empty containers safely.
For pesticide information please call UConn Home and Garden Education Center weekdays, in Connecticut call toll free 877-486-6271. Out of state call 860-486-6271.
Revised by UConn Home and Garden Education Center 2016.
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