Fall Webworms: Webs In Your Trees

Fall Webworms 1

Fall Webworms are a native pest of shade trees and shrubs that emerge throughout mid-late summer and fall. Similar to Eastern Tent Caterpillar which we’ve discussed before, Fall Webworm are caterpillars that weave webs in trees & shrubs while feeding on their leaves.

If left untreated, these insects will defoliate numerous branches and possibly the entire tree. Between the defoliation and giant webs, this pest turns trees into an eyesore.

Species Targeted: Fall webworms target almost all shade, fruit, and ornamental trees except conifers. In the United States, about 90 species of trees are regularly affected. The most susceptible in our area include hickory, walnut, elm, birch, cherry, redbud, willow, oak, mulberry, crabapple and some maples.

Fall Webworms

Fall Webworms Sign & Symptoms:

To spot Fall Webworms keep an eye out for the signs and symptoms below.

  • Webs constructed around leaves at the end of branches
  • Hundreds of larvae, excrement, and dried leaf fragments will be in the webs
  • Webs will make jerking movements when the caterpillars are alarmed.
  • Defoliation
  • Caterpillars on your tree and shrubs
  • Young larvae are pale yellow with two rows of black marks along their body
  • When fully grown, they are covered in white hairs that originate from black and orange spots

You can distinguish webworms from Eastern Tent Caterpillars by where they choose to build their nests and what time of year they emerge. Fall Webworms weave their nests at the ends of branches whereas the Eastern Tent Caterpillar chooses to build its nest in the crotches of tree branches.  Webworms also appear in late summer to early fall while Eastern Tent Caterpillars appear in spring.

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Webworm Lasting Damage:

The good news is that fall webworms typically do not leave any lasting damage. However; once you have an infestation you will most likely have it year after year. This is because webworms overwinter in cocoons found in the leaf litter and bark of trees and shrubs. In the spring they emerge as adults and lay eggs in your foliage. When these eggs hatch they begin to feed on your leaves and build webs, starting the cycle all over again. Yearly infections can lead to lasting damage, slowed growth,  and leave your trees vulnerable to secondary invaders.

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Fall Webworm Treatment:

Thankfully, Fall Webworms are easily controlled using systemic treatments and foliage sprays. Depending on the severity of the infestation, the location of the tree, and the tree species our Arborists will recommend some version of manual removal, treatments to kill the webworms this season, and preventative treatments to keep them from coming back next season.

Book an appointment with an arborist online or call 703.573.3029 if you think you have Fall Webworms.

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