Issue 13, July 30, 2010

Zimmerman Pine Moth

Zimmerman pine moth should be susceptible to control in southern Illinois at this time. Treatment in northern Illinois should occur around mid-August. Permethrin, sold as Astro and other trade names, will be effective for several weeks sprayed on the trunk and larger branches.

Zimmerman pine moth caterpillars feed at branch whorls of Scotch, Austrian, red, and other pines. Damage appears as whitish globules or cones of pitch on the trunk in the area where the branches attach to the trunk. They may also attack at the base of major branches, causing browning of the foliage. Frequently, when trunks are attacked, their feeding weakens the trunk to where it snaps off at that point. Several lateral buds will break and grow, resulting in a multi-leader tree that looks more candelabra-shaped than that of a telephone pole.

The caterpillars are whitish to brownish, with or without dark brown spots. They tunnel primarily just under the bark, making it easy to expose larvae or pupae by breaking off and looking under and in pitch masses. Fully grown larvae are about one inch long. Adult moths are gray, black, and brown patterned, being one-half to five-eighths inch long. Eggs are laid under loose bark. The resulting larvae feed on bark and roam on the outside of the trunk for a few weeks, making them susceptible to an insecticide residue on the trunk. They spend the winter as young larvae in hibernacula under the bark. The caterpillars emerge in April and roam again for a couple of weeks before tunneling under the bark. They are also susceptible to control during this spring roaming phase.--Phil Nixon

Phil Nixon

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