Some 250,000 acres of Maine fir trees are at risk of defoliation from a moth that could cause millions of dollars of harm to the state’s economy if ignored, forestry experts said during a webinar Wednesday. The spruce budworm is an emerging threat that has already been spotted in Aroostook County near the Canadian border earlier this year, affecting some 3,500 acres of trees, according to the University of Maine Cooperative Extension. Forestry experts worry that the spruce budworm could spread quickly and damage up to 250,000 acres of Maine’s forests next year. As part of a webinar sponsored by the Maine State Chamber of Commerce on Wednesday, they recommended early intervention with aerial pesticide spraying starting in May.