The mild winter will lead to high over winter survival of Hemlock Wooly Adelgid. These are host specific insects that feed on the underside of hemlock needles, and in large populations can severely weaken or even kill its host. In a typical winter a prolonged cold spell will kill many of these insects but the lack of cold this winter has not done that. Be sure to check your hemlock trees, especially if they are used in a hedge or other screening situation. Dieback on hemlocks is not something that will re-grow from latent buds like some other species do. The insects are easily identifiable as white cottony masses that will appear on the underside of needles being easily visible when looking at the underside of branches. If you find any on your trees give us a call so that they can be properly treated.