BERWICK — A tiny pest that has devastated hemlock forests from southern Appalachia to New England is steadily spreading in Maine, forcing some landowners to choose between saving and harvesting trees. …“Landowners are going to have to adapt to it,” said Dave Struble, chief entomologist with the Maine Forest Service. …Individual trees can be treated with pesticides to kill or control the adelgid, but such an approach would have been unfeasible or cost prohibitive for an infestation the size of the one in Berwick. Forestry and entomology professionals in Maine also are experimenting with the release of predatory beetles – also from Asia – that feed exclusively on the woolly adelgid. Such natural-control methods are costly, however, and often take years to take root, if they ever do.