October 19, 2018
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Toxic moths are on the move in Maine

They’re little, snow white and fuzzy. Some people are even calling the moths “cute” or “pretty.”

But to people who know what they are, the innocuous-seeming moths are not cute at all. In fact, they can be toxic. Browntail moths are an invasive insect pest that this summer is being spotted in an increasingly large swath of Maine. While the moths themselves are not poisonous, the caterpillars have tiny poisonous hairs that can cause a skin rash similar to poison ivy. In some cases, the hairs may be inhaled and cause respiratory distress.

Still, it can be hard for Mainers to understand that the fluffy, white moths can cause so much distress. And others may simply not want to believe that browntail moths have come to their communities.

“A lot of folks, even though they’re seeing it, they may not be believing that it’s right in their backyard,” Kyle Rosenberg, the Bath city arborist, said Friday of the moths. “I think [the moths have] caught a lot of people off guard.”

Courtesy of Maine Department of Agriculture, Conservation and Forestry
Courtesy of Maine Department of Agriculture, Conservation and Forestry
The Maine Department of Agriculture, Conservation and Forestry is interested in collecting data to track the spread of these browntail moths and caterpillars.

For residents of some coastal Maine communities, including Bath, Brunswick, Freeport and Bowdoinham, the moths are an unwelcome but familiar sight. But this year, they’ve been seen in more distant communities, including Rockland and Belfast, where residents do not always know what they are. This week in Belfast, one of the entrances to the Hannaford grocery store was closed for several hours because so many moths were clustered around the doors that the company needed to have them removed. Also, photos of the moths — and sometimes of the rashes — are being shared on social media as people are trying to figure out is happening in their neighborhoods or to help spread the word to others.

Maine officials also are working to get the word out about the spread of browntail moths, including acting state entomologist Allison Kanoti, who said that this year she’s found moths not far from her Old Town home.

“I’m dismayed at their spread,” she said Friday. “The current footprint of browntail moth is about the same as it was in 1922. It’s been awhile since it was so widespread.”

The moths are first known to have come to the United States in the late 1890s, and are believed to have been accidentally brought to Somerville, Massachusetts, on a load of shrubs imported from Europe. Their spread was fast and relentless. By 1914, they were found from Vermont and Connecticut to New Brunswick and Nova Scotia, and by 1915, the town of Houlton was “quarantined” for the moth by the direction of federal authorities, according to BDN archives. Then, in the 1920s, the population collapsed, for reasons that are still not completely understood.

“There are theories out there,” Kanoti said. “It’s thought to be a combination of weather, parasites and diseases that brought about its collapse.”

By the 1970s, the moth’s territory had nearly disappeared. It was only found on Casco Bay islands and on Cape Cod. Scientists figured that this was one problem that had been licked.

“They thought it was a pest you could eradicate,” Kanoti said.

They were wrong. Beginning in the late 1980s, the population began to grow again. Thirty years later, it seems like the browntail moth’s spread across the state is unstoppable, but there are things Mainers can do that may help, the entomologist said.

People are encouraged to report sightings of browntail moth adults to the state by filling out an online survey at www.surveymonkey.com/r/mebrowntail.

“Just being aware of what an infestation looks like might be a start,” she said. “Right now, the infestation looks like little white moths with brown tails that are attracted to light.”

The moths breed one generation a year and have four life stages: egg, larval, pupal and adult, according to a fact sheet published by the Maine Forest Service.

Right now, Mainers are seeing the adult stage of the life cycle, when the moths, which are strongly attracted to light, lay clusters of eggs on the underside of leaves (and sometimes buildings). Next month, caterpillars will emerge from the eggs and feed on the upper side of the leaves of host trees. In the fall, colonies of caterpillars will build winter webs on the tips of branches, using leaves tightly wrapped with white silk. There can be as many as 400 or more caterpillars in each web, and they overwinter until spring, when they earliest leaf buds open. At that point, the caterpillars leave the webs to feed on tender new leaves. By late June, the caterpillars are fully grown, and then form filmy cocoons for the pupal stage, which is when caterpillars turn into adult moths. They typically emerge from cocoons in late July and August, although this year the transformation to moths has happened earlier than usual.

The most effective time in the moth’s life cycle to do population control is in the winter months, when the webs are most visible, and can be clipped and destroyed by burning them or by soaking them in soapy water. It’s also possible to use pesticides to manage the moths, by applying chemicals to the leaves of host trees, injecting them into the trees or treating the soil.

“There are options for managing browntail moth. But all of them have advantages and disadvantages. None of them are perfect,” Kanoti said. “The best thing you can hope for is to catch it before the population explodes.”

Mainers who may not be used to the moths also are strongly urged to be careful around the caterpillar hairs, which can remain toxic for up to three years. The problem with the hairs is worse from May to July, when the caterpillars are active, according to the Maine Forest Service, but can cause a reaction at other times of year as well. The microscopic hairs break off the caterpillars and can be found everywhere in browntail infested areas, including on trees, lawns, gardens, decks, picnic tables and in the air.

People are encouraged to avoid heavily infested areas, take a cool shower and change clothes after any activity that might involve contact with hair, use caution cleaning debris left by caterpillars, and dry their laundry inside during June and July to avoid hairs getting onto clothing. In heavily infested areas, they should wear respirator, goggles and coveralls when mowing, raking, weed-whacking, removing webbing or otherwise stirring up caterpillar hairs.

Right now, people who see adult moths can try to use a shop vacuum to suck up them up, Rosenberg said. They also can look for the eggs to destroy them, too.

“If they have smaller trees that they can visually inspect, they can look for egg masses, yank those leaves off and dispose of the egg mass,” he said. “They can be put in a garbage bag and then put in the garbage.”

If Mainers see eggs they can’t reach, it’s also a good time to start looking for an arborist who can help them with browntail moth control, he said.

“At the very least, have a professional come in October to assess the amount of nests they have. Earlier is better when trying to get on lists of service providers,” he said. “The greater the expansion of moths to new areas, the greater the demand is. Those service providers fill up quick.”

It sounds like a lot to remember, but the alternative isn’t very good, Rosenberg said.

“I remind people that having a full body rash in the spring can be a very discouraging start to the season,” he said.

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