Eastern tent caterpillar

What is eastern tent caterpillar?

Eastern tent caterpillar is a native moth (PA DCNR) whose caterpillars live together in a silk tent. The tent goes in the fork or crotch of a branch and gets bigger as the caterpillars grow. They hatch very early, right as wild cherry leaves open, and eat new buds and leaves.

When numbers are high, a tree can be stripped bare. UMass says big outbreaks come roughly every 8 to 10 years. Penn State calls the damage mostly cosmetic: healthy deciduous trees can lose all their leaves several years in a row and still recover on their own.

Horse owners should pay attention. Penn State says horses that eat wandering caterpillars have been linked to mare reproductive loss syndrome, so watch host trees near pastures during outbreaks.

People and pets: Hairs can irritate eyes and mouth; wear gloves and wash hands after handling (Penn State). Horses that eat the caterpillars have been linked to mare reproductive loss syndrome.

Signs and damage

• White silk tents in branch forks and crotches in early spring that grow as the caterpillars feed
• Groups of hairy black caterpillars with a white stripe down the back on or near the tent
• Leaves eaten off branches near the tent; badly hit trees look like they never leafed out
• Shiny dark egg bands wrapped around small twigs in winter
• White to yellowish cocoons on host plants, fences and other objects in early summer

Eastern tent caterpillar identification: what to look for

• Adult: Fluffy tan to reddish-brown moth with two pale, slanted stripes on each front wing. Flies late June into July.
• Larva: Hairy. Young ones are dark with thin yellow lines. Grown ones reach about 2 inches with a solid white stripe down the back, yellow side lines and a mottled blue, yellow and black body.
• Eggs: Band of 150 to 350 eggs wrapped around a small twig, dark gray to black, with a shiny coating. Present from summer through winter.
• Damage: Silk tents in branch forks and leaves eaten from nearby branches in spring.
• Timing: Hatch in early spring as wild cherry leaves open; caterpillars pupate in early summer; moths fly late June and July.

Life cycle

One generation a year. Eggs laid in a band around a twig spend the winter there. Caterpillars hatch in early spring, about when wild cherry leaves open, and build a shared tent in a branch fork. They leave the tent on warm days to feed and come back to rest. In early summer the grown caterpillars wander off to spin white to yellowish cocoons in dry, sheltered spots. Moths come out in late June and July, and each female lays 150 to 350 eggs.

When to look: Look for egg bands on bare twigs in winter. Look for small tents in early spring as cherry and apple leaf out. Wandering caterpillars and cocoons show up in early summer.

Eastern tent caterpillar look-alikes

A few things get mixed up with it:

• Fall webworm (Hyphantria cunea): Builds webs at the branch tips that enclose the leaves, in late summer and fall. Eastern tent caterpillar tents sit in branch forks in spring.
• Forest tent caterpillar (Malacosoma disstria): Penn State says it has keyhole-shaped spots down the back instead of a solid white stripe, and UMass says it does not build a web or tent.
• Spongy moth (Lymantria dispar): Grown caterpillars have 5 pairs of blue dots and 6 pairs of red dots and do not build tents.

How to control eastern tent caterpillar

Cultural control

• In winter, prune off twigs with egg bands before they hatch.
• In early spring, pull out small tents by hand or with a stick and throw them away before much feeding happens.
• Never burn tents on the tree; Penn State and UMass both warn against it.
• In woods, Penn State does not recommend control; on ornamental trees, keeping trees healthy and doing nothing is often fine.

Biological control

• Parasites are usually effective (UMass).
• Birds, small mammals, predatory insects and parasitic wasps all feed on the caterpillars.

Chemical control

Penn State says Bt (Bacillus thuringiensis) or horticultural oil can control young caterpillars, and broad-spectrum insecticides are a last resort for older ones. UMass notes that sprays work best on warm days when caterpillars leave the tent to feed, since caterpillars inside the silk are protected, and that applications should come after bloom to protect pollinators. Use only products labeled for this use; the label is the law. For tall trees, use an ISA Certified Arborist or licensed applicator. Muthler Landscaping does not spray or apply pesticides; see our pesticide applicator license guide.

Use only products labeled for this pest and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Check wild cherry, apple and crabapple twigs for egg bands each winter.
• Horse owners: watch host trees near pastures in spring outbreaks.

When to call a pro

Usually not needed; trees recover. Consider an ISA Certified Arborist if a small or already stressed ornamental tree is stripped several years running, or if tents are too high to reach.

Related guides: Tree database: mature size and planting distance · Pennsylvania tree identification · Firewood rules by state · All pests and diseases

Questions about eastern tent caterpillar

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