AUGUSTA, Maine — Three decades ago, an insidious pest called the spruce budworm wreaked devastation on Maine’s forests, defoliating millions of acres of the state’s abundant fir and spruce trees until they were dry sticks.
The infestation, which began reaching its worst stages in the late 1970s, prompted a small-scale air war, first with chemicals sprayed from aircraft and later with biological insecticides. At last, by the later 1980s, the budworms went away.
But experts now say the bugs may soon descend upon Maine again.
‘‘We are taking this seriously,’’ said state entomologist Dave Struble.
Forestry officials are keeping a close eye on Canada, said Struble. There’s been ‘‘a ripping outbreak’’ on the northern shore of the St. Lawrence River in Quebec, prompting an aerial spraying operation, and defoliation is detected on the south shore, he said. In New Brunswick, reports of budworm caterpillars picked up during the summer, but whether they were moving toward Maine isn’t known, Struble added.
Mindful of the cyclical pattern of infestations, Maine foresters have turned up some budworms in traps they set, but ‘‘we don’t know exactly what it means,’’ said Struble. That’s because the best type of trap being used was not around during the last big outbreak.
Budworm larvae bore into and feed on the evergreens’ needles or expanding buds. Gradually the needles turn brown, giving the defoliated tree a scorched appearance, according to the US Department of Agriculture.
After a small wave of budworms came and went in the 1950s and ’60s, taking some trees with it, the state was hit by a tsunami of the pests in the 1970s and ’80s. The invasion was taken very seriously by paper companies that owned vast blocks of forests.
That prompted an all-out attack on the budworms, with aircraft laden with chemical insecticides dispatched for much of the day from outposts in northern and eastern Maine to treat an area the size of Connecticut.
The massive operation also touched off howls of protest from residents of those remote regions, who were concerned about the health and environmental effects of the spray program.