Eastern tent caterpillar
Eastern tent caterpillar is a native caterpillar of wild and ornamental cherry, apple, crabapple and their relatives. In early spring the young caterpillars spin a dense white tent in the fork of a branch. They leave it in the early morning, the evening and at night to feed on the new leaves and enlarge it as they grow. Four to six weeks later they wander off to pupate, and that is when people find them crossing paths and walls. A tree usually recovers and puts out new leaves. In a garden, the practical control is to remove egg masses in winter and small tents in spring.
Malacosoma americanum tent in the crotch of a wild cherry in spring. Photo: pending.
Identification
The tent and the season give it away. Eastern tent caterpillar builds a thick tent in the fork or crotch of a branch in spring, and the caterpillars go out of it to feed in the early morning, evening and night, sheltering inside in the heat of the day and in rain or cold. Fall webworm is the one it is confused with, and it is the opposite on every count: a loose web over the tip of a branch, in late summer and autumn, with the caterpillars feeding inside it. Forest tent caterpillar, a close relative, spins silk sheets rather than a tent, and has a row of white spots down the back instead of a stripe.
The full-grown caterpillar is 2 to 2½ inches long and sparsely hairy. It is black with a white stripe down the middle of the back, brown and yellow lines along the sides and a row of oval blue spots. The egg masses are the other thing to look for: shiny, black, varnished-looking collars that encircle twigs about the thickness of a pencil, each holding 150 to 400 eggs. The moth is reddish-brown with two pale diagonal stripes across each forewing.
Easily confused with
- Fall webwormAlso a pestA loose, dirty web enclosing the ends of branches in summer and autumn, with the caterpillars feeding inside it. Eastern tent caterpillar’s tent is thick, sits in a branch fork in spring, and is left empty while the caterpillars feed.
- Forest tent caterpillarAlso a pestSpins flat silk sheets rather than a tent, and has a row of white spots down the back instead of a continuous white stripe.
- Spongy mothAlso a pestMakes no silk tent or web, and has five pairs of blue dots then six pairs of red dots down its back. It hatches later, in early May in Massachusetts, and feeds into June.
- BagwormsAlso a pestEach caterpillar lives alone in a spindle-shaped bag covered in bits of leaf or needle, hanging from a twig, not in a shared white silk tent.
Damage symptoms
The caterpillars eat the new spring leaves around the tent, and when they are numerous they can nearly strip a tree. Most trees put out a new crop of leaves and recover from one or two years of it. UConn notes that successive years of high numbers can stunt growth and leave trees more open to disease.
- A white silk tent in the fork of a branch in early spring, growing to a foot or more
- Branches stripped of new leaves around the tent
- Caterpillars trailing out along branches to feed in the morning and evening
- In late spring, black-and-white caterpillars wandering across paths, walls and buildings
- Shiny black collars of eggs around bare twigs in winter
Lifecycle & degree days
One generation a year. The eggs spend the winter on the twigs and hatch in early spring: in March in Kentucky and Connecticut. The caterpillars feed for four to six weeks and then leave the tree to spin cocoons in sheltered places.
- Egg hatch
- Early March in Kentucky; March in Connecticut
- Caterpillar stage
- 4–6 weeks
- Cocoon
- Whitish, ~1 in, in a sheltered spot; moths ~3 weeks later
- Generations / yr
- 1
- Overwinters
- Egg masses on twigs
Host crops
Mainly the rose family, with cherry and apple the favourites. The University of Kentucky lists wild cherry, apple, crabapple, hawthorn, maple, peach, pear and plum. UNH notes it is of little economic importance in regularly sprayed orchards but a significant pest of nurseries and landscapes, because the tents are so conspicuous.
Monitoring & action thresholds
No numeric threshold is published for gardens. The University of Kentucky says trees usually recover and put out a new crop of leaves, and the tent is mostly an eyesore. UConn notes that successive years of heavy feeding can stunt growth, so a tree stripped the year before is the one most worth protecting.
In winter, after leaf drop, look along bare twigs of cherry and crabapple for the shiny black egg collars and cut them out. In early spring, as buds open, check branch forks for small new tents. Newly formed tents can be pulled out by hand; larger ones have to be pruned out or wound onto a stick.
Biological control
Braconid, ichneumonid and chalcid wasps parasitise tent caterpillars, and birds, toads, snakes, raccoons and other insects eat them. A naturally occurring virus and a fungus can also kill many of them. None of this is bought. Btk is the purchasable control, and it works because the caterpillars feed on open leaves outside the tent, where the spray lands.
Cultural controls
Hand removal at the right moment beats spraying on a garden tree.
- Cut out the black egg collars on twigs from autumn through winter
- Pull out small tents by hand while the caterpillars are inside: in the heat of the day, or in rain or cold
- Do not burn tents out with a torch or open flame
- Leave wandering late-spring caterpillars alone; they are finished feeding and looking for a place to pupate
Chemical, last resort
Sources
University of Kentucky ENTFACT-423, Eastern Tent Caterpillar (Bessin, rev. 2026)
UConn Home & Garden Education Center, Eastern Tent Caterpillars (rev. 2016)
UNH Extension, Fall webworm & Eastern Tent Caterpillar fact sheet
Bonide Thuricide concentrate label, EPA Reg. 4-226 (2016)
Monterey B.t. label, EPA Reg. 70051-106-54705 (2014)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Eastern tent caterpillar by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.