A browntail moth clings to a picket fence outside the library in Southwest Harbor on Friday, July 13, 2018. Credit: Bill Trotter / BDN

A team of researchers at the University of Maine might have found a way to prevent outbreaks in the future by tricking the moths with their own sense of smell.

“This method involves saturating the air with the female pheromone so the males can no longer find the females within that area,” said Angela Mech, an assistant professor of forest ecology at the University of Maine. “They get confused in the air, so to speak, and with no mating, no egg masses are laid for the following year, causing the population to decline.”

The  browntail moth outbreak this summer has been worse than it has been in over a century, giving Mainers itchy rashes all over the state. This research could help the state prevent an outbreak in the future.

Mech came up with the idea after considering the ways that similar insect outbreaks have been controlled in the past — namely, gypsy moths, which are related to browntail moths. In the 1980s, when gypsy moth outbreaks were causing severe defoliation across the country, researchers developed traps using the moths pheromones, the chemical compounds that the moths release to attract mates.

In this June 2019 file photo, Dr. Jane Robertson of Belfast shows the remnants of a browntail moth caterpillar rash she got on her neck. Credit: Abigail Curtis / BDN

The pheromones won’t smell like anything to humans. Plus, unlike pesticides currently used to manage some browntail moth outbreaks in Maine, pheromones are so specific to the insect they are targeting that they generally don’t impact any other wildlife (or people) in the surrounding area.

“If it works, the environmental impacts compared to the chemicals currently used are substantial,” Mech said. “It’s so specific to browntail moths it won’t have any non-target effects on other butterflies and moths, and the costs can be cheaper for the pheromone than for some pesticides. If effective, it has the potential to be a game-changer in the fight against browntail moths.”

Mech is working with a number of partners to make this project happen, including the U.S. Department of Agriculture Forest Service and the Maine Forest Service. Tom Schmeelk, entomologist at the Maine Forest Service, said that if successful, this could be a new tool used in the management of the browntail moth population.

“The people and citizens of Maine have been sort of inundated with browntail moths and it’s been expanding its range and moving more inland and affecting more people. It is very promising but hopefully will be promising since it has worked for other species,” Schmeelk said.

The method is in the testing stages now. This week, Mech and her team plan to set up 15 sites across the state of Maine to see which pheromone is the best at attracting male browntail moths. Mech said that the pheromone that browntail moths use to attract mates was identified back in the 1990s, so she is working with Trece Incorporated in Oklahoma to create a synthetic version of the pheromone to test this summer.

“Once we are satisfied with the version of the pheromone we want to use, once the pilot study is done this summer, we’ll probably start implementing monitoring and management test sites next summer,” Mech said. “I have already had a lot of private landowners and homeowners volunteer their property for me to set up traps on.”

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Schmeek said that the folks at the Maine Forest Service are “keeping [their] fingers crossed” for good results from the pilot study.

“[If] we have some good results in this pilot year, we can dive in a full fledged experiment next year and then get on the road of possibly using this as a management strategy,” Schmeek said.

Because browntail moths and gypsy moths aren’t identical, there are a lot of questions when it comes to how to effectively implement this technique for browntail moths. The method hasn’t worked on all varieties of insect and moth it’s been tested on, Mech said.

“It can depend on the insect’s behavior and biology. For example, the flight capability of the female — if the females are strong flyers and can escape the plume area of where the pheromones are being released, the males will be able to find them,” Mech said. “Gypsy moth females don’t fly, which is why mating disruption has been a successful tool for that pest.”

Some of the historical data I’ve been finding indicates that [female browntail moths] are heavy and don’t fly far, although they can be carried by the wind, and that they may not disperse until after they have been mated. If these are the case, they would benefit us and hopefully allow the mating disruption pheromone to work better. It’s all of these little pieces coming together.”

Mech is also working with the University of New Hampshire, which wants to quash the browntail moth problem before it gets to New Hampshire.

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“Browntail moths have been detected only 20 miles from the New Hampshire border,” Mech said. “It’s getting close so they have a vested interest in it.”

Earlier this year, Mech and her team received a grant from the Northeastern States Research Cooperative to support the research.

The project doesn’t end at management of the population, though. Eventually, Mech hopes to be able to develop a monitoring system to predict future outbreaks.

Mech said that browntail moths have natural population growth spurts that are cyclical, occurring every 15 or 30 years. The last outbreak in the United States was in the 1990s and lasted for about five years before it was contained naturally by funguses and parasites.  The current browntail moth outbreak started around 2015, but is still going strong.

“The little population bursts have been getting bigger over the last 100 years,” Mech said. “If we think along those lines, we might be having this conversation again in another 15 to 20 years. We don’t want that.”

After the last browntail moth outbreak was quelled in the 1990s, the research on the insect effectively stopped.

“There was some research in the late ’90s and early 2000s with the last little outbreak, but it was naturally contained within a few years so research stopped,” Mech said. “There’s currently no long-term monitoring program in place, so in the future, there would be no way to see if the populations are growing until they reach a level where we start itching.”

The research for the monitoring system will take years, but Mech said that she and her team are working as fast as possible to make this a reality.

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“We all feel the itchy pain,” Mech said. “My fear is that people will be afraid to visit Maine because of browntail moths, which I hope is not the case. As with most pests, it is just a matter of being educated about the risks and preventative measures that can be taken.”

In the meantime, there are some steps that you can take to ease the pressure of browntail moths.

“We recommend turning off your outside lights by dusk from now through August,” Mech said. “Come wintertime, clipping the winter webs that can be reached can help reduce next spring’s itchy episode.”

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