By Winnie Lowsma
WSU Master Gardener 

Fall web worms cover leaves as they dine


September 26, 2019

Rick Nelson

Web worms set up their tents on local trees.

Fall is here, the tree leaves are drying and rattling in the wind. Already many are drifting to the ground. Looking up to the canopy, you can observe the wispy nests of the fall web worm. In late summer and early autumn the web worm moth may lay as many as 100 eggs on the underside of leaves, near the tips of branches.

In about a week the eggs hatch. The caterpillars spin out their silk to protect themselves from birds and other predators. The webs cover the leaves that the caterpillars eat. At first the caterpillars eat the surface of the leaves. As the first leaves are eaten, the caterpillars expand their silken nest to cover more leaves.

The moth is about the size of a miller moth, is snowy white, some have downy like fuzz on the thorax, some do not, some have a variety of black spots, and all are very pretty moths. The moths don't generally inhabit buildings and do not harm structures.

The caterpillar grows to about one inch, has a yellowish stripe along its sides and has several rows of spikey setae (whiskers or stiff hairs). The larva then drop to the ground where they pupate over the winter. The webs disintegrate in the wind and rain.

These caterpillars consume leaves that the tree would soon shed in the fall months and do not seriously harm a healthy tee. Some people feel that webs are unsightly, they can be removed with a pole or water jet or just opened up for the birds to eat, and to that end, and they could possibly be considered beneficial. For more information on Fall Webworm:

You may be interested in the Tent Caterpillar which appears in the Spring and is different from the Fall Webworm. Wikipedia has information on them also.


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