A spruce budworm outbreak has plagued Maine’s northern borders for nearly two decades, with the tree-killing moths making sporadic incursions from Quebec but never reaching numbers that suggest a repeat of the outbreak that ravaged the state a half-century ago. This summer, though, state entomologist Michael Parisio surveyed the northwestern woods of Aroostook County by plane. A 3,000-acre hot spot of partially denuded spruce-fir forest suggested the once-a-generation outbreak everyone had feared might have begun. …”We’ve had a few scares here and there, but 3,000 acres, that’s significant damage,” Parisio said. “All evidence suggests it will persist and expand. We knew it would get here eventually, but knowing doesn’t make what’s going to happen any easier.” University of Maine modeling shows that more than 178,000 acres are on the verge of defoliation. …The last outbreak lasted from 1967 to 1993, covering 136 million acres across eastern Canada and Maine.