Browntail
moth--an invasive species whose caterpillars have toxic, irritating hairs—is
found at varying population densities over more than 6500 square miles of Maine
(see map here: http://www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm). It is a pest that has hunkered down in the
Midcoast and Casco Bay area for years, and has recently expanded its
footprint.
People
looking to reduce browntail moth populations may look at the cocoons as an
opportunity for reduction. However, you will
have limited impact through cleaning cocoons.
Safer, more effective control will be had through targeting larvae,
either in overwintering webs (put a reminder in your calendar now to look for
those structures at the tips of host branches around your property this fall
and winter!) or as they feed on host leaves in early spring.
You may still
want to remove the cocoons to limit potential for exposure to the toxic hairs
they contain. However, do this with extreme caution. Cocoons
are full of the hairs THAT CAN CAUSE A RASH or worse. If you plan to remove cocoons:
- Wear protective clothing (in addition
to long sleeves, pants, socks, socks, shoes, gloves, mask and glasses, consider
protective coveralls)
- Wet
down cocoons before removing them
- Scrape
cocoons and drop them in soapy water, let them soak overnight then dispose of
them
Even if you don’t plan to remove
cocoons, become familiar with their appearance, and learn to avoid them or wear
appropriate protective clothing during your outdoor activities that might bring
you in contact with them.
Browntail moth caterpillars wander and
form their cocoons anywhere. Favorite places include: Under the eaves of
buildings or the undersides of anything (reports include vehicles, and even a
baby stroller) and wrapped in the leaves of any plant.
Traveling within the cocoons on
vehicles, outdoor equipment and other items (including firewood), is a very
efficient means of spread for this moth. If you have plans to travel between the affected and unaffected areas over
the next month, check your belongings closely for these cocoons. This winter, be on the lookout for the tell-tale
webs in new places—these are the places where control will be most effective!
Contact: Forest Health and Monitoring, (207) 827-1813
Larvae forming cocoons under eaves of a building. Photo: Maine Forest Service, DACF
Invasive browntail moth cocoon wrapped in invasive common buckthorn leaves beneath defoliated bur oak (Bangor, ME, June 20, 2018). Photo: Maine Forest Service, DACF.
Browntail moth cocoon with several pupae in defoliated bur oak (Bangor, ME, June 20, 2018). Photo: Maine Forest Service, DACF.
Large communal pupal masses on oak. Photo: Maine Forest Service, DACF
Two cocoons inside webbing under a picnic table. Cocoons look similar to spider egg sacs. Photo: Maine Forest Service, DACF
Late-stage browntail moth caterpillar on American elm (Bangor, ME, June 20, 2018). Photo: Maine Forest Service, DACF.
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