Residents of Rosetown may have noticed clusters of webs causing brown, dead patches on some trees in the last little while. These unsightly webs may be the nests of a caterpillar called a fall web-worm (Hyphantria cunea).


Web-worms are caterpillars that weave loose webbing around the tree’s foliage, resulting in plant stress and leaf loss. The larval nest may cover single leaves or leaf clusters, or in many cases, entire branches.

‘The web-worm caterpillar is about an inch long with a black to reddish head and light yellow to greenish body with a mottled stripe of two rows of black tubercles and tufts of long whitish hairs. Adults appear as white moths with dark spots on the wings.’

The web-worms will spend their larval state inside these nests, feasting on the encased leaves. As the leaves are devoured, the webbed nest will be expanded to fresh foliage. The impact of these pests is usually fleeting and strictly cosmetic.

Crab Apple trees and other ornamental, fruit and nut trees have been hit with this pest. Experts say that the good news is that these caterpillars are not nearly as destructive as spring Tent Caterpillars. Tent Caterpillars occur much earlier in the year and are a different pest all together.


A few options for dealing with web-worms include:


1) Do nothing... especially for any that are occurring high up or in difficult to reach positions.
2) Break open the nests with a stick, rake or long pole, which makes it easier for birds or other natural predators to take care of the caterpillars.
3) Apply BTK insecticide or a more toxic insecticide such as Malathion.