Question
Jim - I live in the southeastern corner of PA.  I live in a wooded setting. About a month ago I noticed what looked like a pure white fungus covering some small limbs of a beech tree in my yard.  It looks like the branch is covered in a fluffy white mold no more than 1/8" thick. After a closer look it seems like it could be many insects all huddled together but I have not gotten that close to it. There is a noticeable discharge from the covered branch that has killed the foliage below and has stained the ground a grayish color.  It also seems that bees are attracted to whatever is falling from the area.  
More recently, I have seem many infected trees around my home and in the woods behind my home. All of which are Beech trees.  I could take a picture and send it to you if you would like.
Please let me know if I should be alarmed. There is a film that is on some of my skylights from what ever this is as well.

Answer
Sounds like Wooly beech Aphids.
Pale yellow, sap-feeding aphids, which are covered by fluffy white fibres, form dense colonies on young shoots and the undersides of leaves. Winged aphids, which have a bluish-white appearance when in flight, fly from infested plants in midsummer in search of other beech trees. These winged aphids are sometimes mistaken for another type of pest, known as whitefly, but whitefly do not infest beech trees and hedges in Britain.

The foliage becomes sticky with the honeydew that is excreted by the aphids and can develop sooty moulds. In heavy attacks the foliage at shoot tips is distorted and leaves may dry up.

The woolly beech aphid gets its name because the body is covered with waxy wool-like filaments. These aphids are gregarious and tend to congregate primarily on the undersides of leaves. Often large numbers of the molting or cast 搒kins?will be attached to leaf hairs, which gives the leaf a whitish appearance. The woolly beech aphid has piercing-sucking mouthparts, which are used to remove plant fluids. However, woolly beech aphid is not considered an economic pest because beech trees, especially large specimen types, can sustain large populations without suffering any injury. Large populations of woolly beech aphid can, however, produce tremendous amounts of honeydew, a clear, sticky liquid that may attract wasps, ants, or yellowjackets. In addition, the honeydew serves as an excellent growing medium for black sooty mold fungi. Black sooty mold fungi can detract from the aesthetic appearance of a beech tree and most importantly can reduce the production of food via photosynthesis by blocking the entry of light.

For large beech trees, control is typically not warranted. A hard spray of water will dislodge aphids from the tree without harming any natural enemies. Insecticides that will provide control include acephate (Orthene), imidacloprid (Merit), and insecticidal soap.