Browntail moths are down, but not out – Remove winter webs before April
Browntail moth (BTM) aerial surveys revealed a decrease in populations in some areas of the state; however, there are still some towns that have high concentrations of winter webs. These include areas in towns surrounding Sebago Lake, communities in a line from Livermore Falls to Falmouth, and communities in Dedham.
It is not unusual to have single trees or clusters of trees with elevated populations amongst areas with low populations due to the caterpillars’ hitchhiking nature. Communities that have BTM winter webs in their trees should make plans to remove and destroy the webs before April. Clipped BTM webs can be destroyed by soaking them in a bucket of soapy water overnight or by burning them in a contained fire – read our Winter Checklist for Browntail for tips on how to manage BTM in the winter.
If winter webs are not removed and destroyed before next month, the caterpillars will emerge from the winter webs and begin feeding on host trees, causing defoliation and increasing risk for their hairs to cause an irritating rash in humans. Even small numbers of webs can result in thousands of wandering caterpillars come spring (there are dozens to several hundred caterpillars in each web).
There are only a few weeks left to remove BTM winter webs before the caterpillars emerge in mid-April.
Image: Leaves that do not fall from the tree in the winter are called marcescent leaves (green arrow). BTM winter webs are leaves that are tighly bound together with white silk – an appearance that makes them stand out from single marcescent leaves (red arrow).
BTM winter webs are roughly 2-5 inches long and are made up of a couple leaves tied together with white silk at the tips of host tree branches. Some trees, like oak, have a tendency to hold onto their leaves in the winter instead of letting them drop in the fall season, a phenomenon known as marcescence. These marcescent leaves can sometimes be mistaken for winter webs – but winter webs have a distinct white silk attaching them to the tree while marcescent leaves do not. This is why we recommend to look for winter webs on a sunny day so that you can tell the difference!
Read the new featured article “The Ups and Downs of BTM” from Northern Woodlands:
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