You see them all over the Lehigh Valley: those unsightly webs on the ends of tree branches.

It’s the fall webworm, not to be confused with the eastern tent caterpillar, which hatch out in early spring.

While each can concern homeowners, healthy trees can withstand the defoliation and should recover without intervention.

The fall webworm, a widely-distributed native pest of shade trees and shrubs, appears from late summer through early fall.

It feeds on almost 90 species of deciduous trees, commonly attacking hickory, walnut, birch, cherry and crabapple.

The fall webworm acts similarly to the eastern tent caterpillar. The fall webworm constructs its nest over the end of the branch rather than at tree crotches. The large conspicuous webs contain caterpillars, dead partially-eaten leaves and fecal droppings.

White hair-covered egg masses contain several hundred light yellow eggs of the fall webworm. Young larvae are pale yellow with two rows of black marks along their bodies.

When fully-grown, they are covered with whitish hairs that originate from black and orange warts.

Larvae vary as to their coloring and markings, but are usually greenish with a broad, dusky stripe along the back with a yellow stripe along the side.

The pupal stage is brown. Adult coloration varies considerably from pure white to white with black spots.

The fall webworm overwinters as a pupa in a cocoon that is concealed in ground litter, cracks and crevices, or in the soil.

Adults first appear in mid-June but may continue to emerge in small numbers during most of the summer. Females usually deposit their egg masses on the undersurface of the leaves.

Larvae hatch in approximately seven days. They immediately begin to spin a small silken web over the foliage on which they feed. As they grow, they enlarge the web to enclose more and more foliage.

The remains of these nests may persist through winter. The webs may sometimes surround two to three feet of infested branches. Mature larvae leave the web and pupate on or in the soil.

The larval stage of the fall webworm skeletonizes and consumes leaves inside the protection of a tent-like web that they enlarge as they require additional food and grow. They may defoliate a tree occasionally, but rarely kill it.

On shade trees, webs usually occur on occasional branches. They may not injure the tree, but they reduce its ornamental value.

Natural enemies help to manage this native insect. Birds and many insect predators and parasitoids attack the larval stage.

It is possible to reduce this pest’s population by mechanical control. When the webbed branches are within reach, they can be pruned and destroyed.

This may be practical if the webs have not become too large and the aesthetic shape of the woody ornamental plant is not reduced by pruning.

If a chemical control is warranted, apply a registered insecticide when webs and larvae are small. This usually occurs sometime in July.

The entire infested plant does not need to be treated. Only the webs and their associated foliage should be thoroughly covered.

Eastern tent caterpillar tents occur in the crotches and forks of branches in spring and early summer. Caterpillars of all sizes use the web tents for protection from predators and parasitoids and feed on leaves away from the tent.

When caterpillars mature in early summer, they migrate away from the tent to find a protected place to spin a cocoon and pupate. Adults emerge in late June and July and lay eggs. The eggs overwinter.

If caterpillars are abundant, they can completely defoliate an infested tree. Because they hatch early, they may consume all the fresh buds and leaves, which gives the appearance that a tree did not leaf out.

Healthy deciduous trees can withstand total defoliation multiple years in a row without long-term detrimental effects. It is not recommended to attempt to control caterpillars in natural forest settings. For ornamental trees, one option is to keep trees healthy and do nothing.

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613.