Spruce budworm. Credit: Courtesy of Neil Thompson

PRESQUE ISLE, Maine — An Aroostook County military air base teemed with war preparations a decade after it closed to fight a tiny forest pest that is making its way back in the 21st century.

In its heyday during World War II and after, the Presque Isle Air Base was a hub for aircraft heading to and from foreign airspace before it closed in 1961. But in the 1970s, repurposed warplanes converged at the airfield to battle a new enemy — the spruce budworm.

PRESQUE ISLE, Maine — March 11, 2022 — This unidentified group of aerial pesticide spraying personnel pose in front of a Lockheed P-2 Neptune, or P2V, aircraft during the June 1972 spruce budworm eradication program in Presque Isle. The plane was one of several former World War II aircraft that were used in the effort. (Courtesy of Dick Graves and Maine Forest Service)

The voracious insects chewed through nearly 136 million acres of spruce and fir in Maine and eastern Canada in the 1970s and 1980s in the largest spruce budworm epidemic ever recorded, according to a report from the Maine Spruce Budworm Task Force. The Maine Forest Service launched a massive aerial spraying program from Presque Isle to eradicate the pests. But they proliferate in 30- to 60-year cycles, and experts see signs that budworm damage is on the rise again.

Eastern spruce budworm caterpillars primarily feast on the buds and needles of fir and spruce. Their numbers are insignificant most years, but periodic population surges can lead to epidemic infestations. Budworm populations began multiplying drastically around 1967 and then exploded.

“Nothing really caused it. It was natural,” Lloyd Irland, president of consulting firm The Irland Group in Wayne, said Thursday. “Just like there’s no real cause of a major flood. It’s something that’s going to happen now and then.”

Irland spent 10 years as Maine’s forest insect manager, then director of public lands and state economist. He directed the Presque Isle spray program for the Maine Forest Service. In those years, northern forests were full of healthy balsam fir trees that were 30-40 years old — the perfect age for budworm feeding.


The Presque Isle base easily became “Budworm Central,” with runways long enough for fully loaded insecticide tankers and space to service planes, Irland said. And the city could accommodate flight crews, contractors and Forest Service personnel — some of whom, including himself, stayed in dormitories at the University of Maine at Presque Isle.

Around 15 planes were based there in a given year, Irland said. Presque Isle was the nearest airstrip that could handle the large planes needed to reach northern Aroostook and Canada.

An on-site meteorologist helped crews pinpoint spraying times. Pilots would fly above the forest in blocks about 30 miles long, spraying pesticide in 80-foot swaths. They covered around 3.5 million acres in 1976 alone, Irland said.

While DDT was used in the 1950s and 1960s, Maine banned it for budworm use in 1967. The late 1960s and 1970s saw pesticides like fenitrothion, mexacarbate, carbaryl, trichlorfon and acephate, according to The Spruce Budworm Outbreak in Maine in the 1970s, a 1988 Maine Agricultural Experiment Station bulletin which Irland co-wrote.

The spray program lasted for roughly three weeks each spring, from the mid-1970s to early 1980s. Public fascination was so great that roadways at the base would be lined with vehicles as people watched the planes take off and land.

PRESQUE ISLE, Maine — March 11, 2022 — Two TBM aircraft spray pesticide over Aroostook County forest during the 1970s spruce budworm spraying program. The Grumman TBM Avenger torpedo bomber was one of several World War II-era models modified for aerial pesticide application. (Courtesy of Dick Graves and Maine Forest Service)

Interest was high because many of the planes used were large four-engine World War II aircraft converted to apply pesticides.

Many of the military planes had flying time left after the war concluded, Irland said. In the early 1970s, the U.S. Department of Defense decided to sell some of them, and spray contractors were among the buyers.

“The really spectacular ones were the Constellations. They had power, speed and were safe and reliable. Those were filled with tanks and they put spray bars and nozzles on the wings,” Irland said. “The next size were the C-54s, which had been successful cargo planes and could carry a lot of insecticide.”

There were also two-engine P2V patrol planes, Grumman TBM Avenger torpedo bombers and at least one B-17 bomber in Presque Isle — a famous WWII-era aircraft called the Flying Fortress, Irland said.

By about 1980, the era of the large spray planes had drawn to a close with the advent of smaller aircraft that could be launched closer to application sites.

But nature prevails, and spruce budworm, which has been in northern forests for thousands of years, is rising, according to the state’s 2021 Spruce Budworm in Maine report. Though experts can’t say when an outbreak will happen, the strategy to combat it will be on a much smaller scale.

Monitoring is key, Michael Parisio, forest entomologist with the Maine Forest Service, said Friday.  The forest service and partners like land companies conduct pheromone trapping to catch moths. The University of Maine Forestry Research Unit observes budworm larvae present through the winter.

Budworm populations began fluctuating in 2013. A huge increase in 2019 was mostly due to migrating moths from a multimillion-acre outbreak in Quebec, Parisio said. Numbers have receded again for the past two years.

Effective monitoring lets experts plan early pesticide treatment. Last year, northern Aroostook County areas were treated after foresters observed actual tree damage.

“[The year] 2021 was the first time we’ve seen [damage] during aerial surveys, to the degree we can actually see it with the naked eye from an airplane,” Parisio said.  

Spots being evaluated now are in far northwest Aroostook on the Quebec border and the Cross Lake area.

But the size of the massive 1970s spray program is unlikely to be seen again, Parisio said. Today there is less balsam fir, and spruce and fir are spread out rather than concentrated in large swaths.

In addition, pest management technology has changed a lot in 50 years. Large planes have been replaced by rotor-winged helicopters, which use modern tools like geographic information system mapping to pinpoint application targets.

The most prevalent insecticide used today on budworm is BTK — bacillus thuringiensis/kurstaki variant — a natural biological pesticide derived from a soil bacterium, Parisio said. BTK is much more environmentally benign than chemicals used 50 years ago because it dissipates within days or weeks and only targets the specific insects.

Overall, Maine is emulating Canada’s early intervention approach.

“We’re certainly aware of what could happen, so we’re as ready as we could be,” Parisio said. “But you just never know what’s going to happen from year to year.”