One of the most effective things to use is Bt, bacillus thurengiensis. It is sold as Dipel dust or Thuricide, a liquid. I prefer the liquid, as it's easier to apply. It's a bacterial pesticide, and is toxic only to catterpillars. Other than that, you can pick off the webs or infected leaves and drop them in soapy water. It won't hurt to pick some leaves, if they're only on certain ones.

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Dave
Even my growlights are getting restless!