"A tiny insect is literally sucking the life out of hemlock trees in the Eastern United States. The hemlock wooly adelgid was first spotted in Virginia in the 1950s. Since then it's hit roughly half the hemlocks from Georgia to Massachusetts. Some beloved old groves, likes those that shaded streams of Shenandoah National Park, are gone. Now the little adelgid is headed north. Emily Guerin tagged along with an entomologist in York, Maine, to see how scientists in the nation's most forested state are trying to keep the bug at bay."