Caterpillar – What to know about browntail moth caterpillars
While the season for browntail moth caterpillars is almost over, Midcoast residents should continue to be vigilant into the summer. Preventative measures can be taken in the next winter season.
Tom Schmeelk, pronounced like elk, is a forest entomologist with the Maine Forest Service and an expert in the browntail moth caterpillar.
This caterpillar is an invasive species that create nests or webs in trees and emerge from the webs in April. They also shed hair that is toxic to humans, and causes painful and itchy rashes.
This year, Schmeelk said, caterpillars emerged from their webs earlier than usual because of warmer days in early spring.
At this stage in their life cycle, the caterpillars are easier to notice, but more difficult to deal with, according to Schmeelk. Midcoast residents may notice the defoliation, and the caterpillars themselves are larger and easier to spot.
There are few treatment options for the caterpillars at this point, though.
Schmeelk said if residents see the caterpillar around, on cars or houses, they can be disposed of with a wet/dry vac with soapy water. This will kill them and prevent them from spreading toxic hairs.
The caterpillars will only be caterpillars for a few more weeks, and then they will go into a cocoon and emerge as a moth. While the cocoon also sheds the toxic hair, adult moths do not.
Once moths emerge, occurrences of the browntail moth rash should decrease. However, Schmeelk said dry weather this spring could cause continued problems.
Toxic hairs that are shed by the caterpillar can rest on top of brush long after the caterpillars metamorphosed, due to a lack of rain. Schmeelk said rain causes the hairs to be incorporated into the soil, so they cease to cause the irritating rash.
Midcoast residents who live near areas of high infestation should be sure to wear long pants and long sleeves when doing yard work, as well as masks and gloves. This will prevent ticks and browntail moth rash.
At this point in the season, Schmeelk said most of the damage has already been done by the caterpillars.
Pete Lammert, Thomaston’s Tree Warden, said an easy way to spot caterpillars are the two bright yellow or orange spots toward one end. While other caterpillars are brown and furry, only the browntail has the two spots.
Lammert said if residents notice defoliation from the caterpillars in their trees, it is important to leave the tree alone and allow it to heal itself.
“Don’t panic if you see severe defoliation in a tree,” Lammert said. “Leave them alone.” Chances are the tree will grow back next year just fine.
The best treatment for these pests is prevention.
From January to March, residents should look for the browntail moth caterpillar web on their trees, Schmeelk said. They can be best spotted on a bright sunny day, at the tip of the branches. The webs are the size of the palm of the hand, and will shine white in the sunlight.
If you see webs during this time, they can be destroyed. Schmeelk said to clip out any webs that can be reached, and either leave them in a bucket of soapy water overnight or burn them in a burn barrel or a wood stove. Burning the webs will not release toxic hairs.
If the webs are higher than can be reached with clippers, residents can schedule pesticide treatment for spring. These services usually fill up fast, so those in need should call before April.
Pesticide treatments are not terribly effective at this current of year, as the caterpillars have left the web.
Schmeelk said the Maine Forest Service website contains details about which pesticides to use.