Maine’s Beech trees have been under attack for decades by beech bark disease that typically appears as disfiguring cankers on a tree species that’s supposed to have a smooth and silvery bark. Affected trees grow slowly and can survive for years. But the diseased beech produce few beechnuts, a loss of an important food source for the Maine black bear.
According to University of Maine researcher William Livingston of the School of Forest Resources, warmer winter temperatures from 1999 to 2002 allowed populations of the invasive, bark-feeding scale insect to explode and incite a more lethal stage of the disease. Insect feeding and the severe drought at that time weakened the trees’ resistance to fungal infection, and many trees died, including those along the Quebec border that were previously unaffected by the disease.
Livingston and Matthew Kasson, a former UMaine graduate student now at Pennsylvania State University, reached these conclusions after sampling hundreds of trees in the affected area. After 2002, typical sub-zero winter temperatures and normal summer rains returned, and the scale populations disappeared. However, the damage was done and beech died from 2003 to 2005, say Livingston and Kasson, who published their findings in the journal Forest Pathology.