Browntail Moth Update, April 29, 2022

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Maine Forest Service

Browntail Moth Update, April 29, 2022

During the week of April 11 we received our first report of newly emerged browntail moth caterpillars basking on the outside of their webs. The following week we had two more observations and have confirmed emergence at some of our monitoring sites this week (see photo). At other sites, caterpillars were not basking due to the inclement weather. Browntail moth caterpillars will feed on the buds and newly emerged leaves of host trees and shrubs now through the end of June.

Browntail caterpillars lounging on the outside of a winter web

Browntail moth caterpillars have broken hibernation and been seen basking on webs from Old Town to Brunswick (Brunswick, Maine,4/26/2022)

Caterpillar diseases are present in the environment and this spring we are seeing some evidence of their activity from late last summer. If environmental conditions this May and June are right (consistent spring moisture) diseases could lead to localized browntail moth population collapses. People should not count on disease-related collapses to save them from the rash. Please plan ahead for avoiding exposure to hairs and treating symptoms related to exposure.

Where population management has been deemed necessary, plans should be in place. By this time web removal should be completed. For pesticide treatments like spraying, it is still too early in many locations, however for some treatment approaches and in some regions the time is now. We recommend working with a licensed pesticide applicator for this management approach. In most years, treatments should be completed before the end of May to limit buildup of toxic caterpillar hairs and host foliage loss.

Contact 211 Maine for answers to frequently asked questions on browntail moths:

  • Dial 211 (or 207-874-2211)
  • Text your zip code to 898-211

Or visit our website

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