The swarm descended on the city in New Brunswick, Canada, in a winged mass so large it was visible on radar, blanketing cars, trees and pavement like some scene from the Bible or a Stephen King novel.

Now experts in Canada and Maine are trying to figure out what last week’s massive swarm of spruce budworm moths means for the timing of the next anticipated outbreak of a pest that killed millions of acres of Maine forestland several decades ago.

“The concern is very, very real and justified, but not every moth (swarm) will result in an infestation in that area,” said Dave Struble, chief entomologist at the Maine Forest Service and an expert on the spruce budworm.

Residents of the Campbellton-Dalhousie area of northern New Brunswick woke last Monday to find their communities – located 120 miles northeast of Caribou, Maine – had become unwitting hosts to untold millions of spruce budworm moths overnight. Although the research continues, entomologists believe the swarm rode the warm, summer winds and air currents more than 130 miles from southern Quebec to this corner of New Brunswick.

Spruce budworm moths cover a parking lot in New Brunswick, Canada.

Spruce budworm moths cover a parking lot in New Brunswick, Canada. (Photos by Joris Wiersinga/Forest Protection Ltd.) Joris Wiersinga/Forest Protection Ltd.

The tan-colored moths filled trees, covered window screens and created winged clouds around lights, according to videos and news reports of the unusual incident. Afterward, some businesses had to hire vacuum trucks to clean up the piles of dead and dying moths literally blanketing the ground.

“They were everywhere and on everything,” one business owner, Dawn Kenny of the Stewart House bed and breakfast in Dalhousie, told The Canadian Press. “There were thousands and thousands of them. They were flying in the air in swarms, especially by the lights. Any place with lights, if you walked by, you’d have to push your way through with your hands to get them out of your face.”

Swarms of spruce budworms moths are not unprecedented, although they are by no means common. Struble remembers seeing “a complete snowstorm” of moths in northern Maine in the 1970s.

The spruce budworm is a native resident of the regional ecosystem and is often barely noticeable. But every 30 to 60 years, the budworm experiences a cyclical population explosion. The last major infestation in Maine occurred in the 1970s and 1980s, destroying an estimated 20 percent of the spruce and fir stands throughout Maine’s commercial forestlands and causing hundreds of millions of dollars in economic damage.

But modern technology and monitoring programs are giving scientists ways to track swarms as well as the steady spread of the destructive spruce budworm in ways that were not possible decades ago. That could help government agencies, landowners and forest managers prepare for the pest’s all-but-inevitable arrival.

“This is a relatively rare event where we actually have the infrastructure in place to study it in a meaningful way to figure out what this means,” said Rob Johns, a New Brunswick-based forest insect ecologist with the federal agency Natural Resources Canada.

PICKED UP ON RADAR

For instance, Canadian weather radar apparently picked up the swarm moving from Baie-Comeau, Quebec, and across the St. Lawrence River to the Campbellton area. (The lack of precipitation at the time – combined with the well-established spruce budworm infestation in the Baie-Comeau area – makes scientists fairly comfortable that they were seeing moth clouds rather than rain clouds.)

Additionally, Natural Resources Canada and the Maine Department of Agriculture, Conservation and Forestry have enlisted large numbers of private landowners to maintain traps that draw in moths as a way to monitor the budworm’s spread. Those traps suggest that the fingers of the swarm may have extended as far south as Saint John, New Brunswick, and potentially extended into Nova Scotia.

“The big question is what does this mean for the outbreak?” Johns said.

A massive swarm of spruce budworm moths clings to a tree in New Brunswick, Canada. Entomologists believe the swarm was carried more than 130 miles on warm summer winds. "They were everywhere and on everything," a business owner in the area said.

A massive swarm of spruce budworm moths clings to a tree in New Brunswick, Canada. Entomologists believe the swarm was carried more than 130 miles on warm summer winds. “They were everywhere and on everything,” a business owner in the area said. Photos by Joris Wiersinga/Forest Protection Limited

Another concern is that the majority of moths analyzed by Natural Resources Canada so far have been female, increasing the possibility that the moths deposited eggs in the area.

Struble had not heard of any swarms or “moth flights” in Maine involving the budworm, although he said most of the moth traps on private lands will not be collected and counted for a month or so. The entomologist said Friday that he is also still waiting for data on the traps that are checked on a weekly basis to detect seasonal fluxes. And he added that a moth swarm that descends on a patch of forest with no people or lights could easily go unnoticed.

Immediately after the Campbellton swarm, the Spruce Budworm Tracker Program and the Health Forest Partnership in Canada sent out an appeal to foresters in northern Maine to collect moths near lights at their homes or camps in the woods. The appeal asks participants to collect moths near lights in a bag – along with pertinent date and geographic information – and then place the bag in the freezer for later collection and analysis.

But spruce budworm numbers are already rising steadily in Maine. Traps throughout northern Maine have seen a steady uptick in insects in recent years.

Areas of Quebec just 50 miles from the Maine border are already experiencing “severe defoliation” and there are smaller pockets of infestations as close as 25 miles from the state. Struble said he wouldn’t be surprised to start seeing signs of budworm infestations on the ground in Maine in the next two to three years, with defoliation visible from the air within three to five years.

“It’s not a reason to go into full alarm in Maine, but people should be concerned and should be thinking about it,” he said.

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During Maine’s last outbreak in the 1970s and 1980s, the budworm decimated the equivalent of 20 million to 25 million cords of wood, or 21 percent of the state’s spruce and fir. The extensive defoliation prompted landowners and the state to clear-cut large areas or apply huge amounts of insecticides, which in turn led to a public outcry and major changes to Maine’s forest practices laws.

A recent report estimated that Maine could lose from 247,000 to 494,000 cords of wood annually – with an economic impact of between $397 million and $794 million per year – if steps are not taken to mitigate the effects of the spruce budworm. The report recommends, among other things, harvesting more trees in high-risk areas now, exploring markets for salvaged trees that are of lower value and exploring policy changes regarding harvesting practices and insecticide application to help landowners during an outbreak.

The report prepared by the Maine Forest Service, the University of Maine and the Maine Forest Products Council is available at sprucebudwormmaine.org.