Your description sounds like the appearance of pine bark adelgids (Pineus strobi) on your white pine. These insects are present on most white pines and you can see their white, wooly tufts on trunks, branches, twigs and even needles, sometimes giving the woody parts of the tree a whitewashed appearance. The adelgids overwinter on white pines (and other pines) as immature insects before beginning to feed in spring. At that point the insects cover themselves in the waxy, wool substance for protection before egg-laying commences in mid-spring. They can reproduce numerous generations per year, with life phases overlapping on a single pine.

A light infestation is common, typically tolerated, and unlikely to cause real damage to an otherwise healthy tree. But the insects feed by piercing the tree and removing fluids from the phloem layer so extreme populations may be a concern.

If you are concerned about the number of insects on your pine, spraying the tree with a forceful jet of hose water can often dislodge a significant number of the insects.  For additional help, consult a certified arborist to examine the infestation and determine whether horticultural sprays should be applied. You can determine the type of preparation that is licensed and effective in your region by contacting your county's cooperative extension office.

Courtesy of NYBG Plant Information Service