Win the War on Webworms: Try these Methods

They’re everywhere. You know what I’m talking about – those ugly, nasty webworm nests insidiously attacking our pecan, mulberry and fruit trees. How can a homeowner stop this multi-legged menace?

First things first, know your opponent. Webworms are not worms at all, but rather caterpillars that turn into moths. The female lays eggs in early March on her preferred tree and shrub species. The caterpillars create a silken web to protect them from their enemies – birds and wasps.

Another important fact, webworms generally don’t search outside the web for food; they build the web around leaves and then eat them. Consequently, the web hinders natural control by predators and prevents effective treatments by humans. Note to self: Destroy the web and you eliminate the webworm.

Here are a few options:

  • Prune off the nest in early spring and on lower branches.
  • Break open the webs with a long stick to allow birds and wasps to eat the little buggers. Wasps can be quite voracious and eliminate a nest overnight.
  • Use insecticides containing Bacillus thuringiensis (Bt), spinosad, or carbaryl. Always read the labels carefully and use as directed.

Finally, I’ve received countless phone calls and e-mails over the years from desperate, agitated homeowners. For the record, webworms don’t pose a threat to tree survival. A nuisance, yes, but they themselves cannot kill a tree. Only repeated severe infestations adversely affect a tree’s health. So don’t lose any sleep over these creatures. I don’t.

Picture of Mark Peterson
Mark Peterson
Mark A. Peterson was a conservation project coordinator for San Antonio Water System before retiring. With over 30 years of experience as an urban forester and arborist, Mark is probably the only person you know who actually prunes trees for fun. When not expounding on the benefits of trees and limited lawns, you're likely to find him hiking San Antonio's wilderness parks or expounding on the virtues of geography and history to his friends.
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