You might notice twigs on beech trees covered in a woolly sleeve. Get closer and it will begin to wiggle and sway. This is a group of beech blight aphids (

). These are very fun to watch and a great way to engage kids and other folks in nature. They are not typically damaging to trees but do create a lot of honeydew that may create patches of sooty mold on the ground. The year after a twig is infested the twig may have some black irregular structures. These can easily be pruned from trees. If the aphids become bothersome a stream of water or horticultural soap or oil will dislodge them.