Pine Needle Scale

Pine needle scale is a very common pest found in the US. It affects mostly Scotch and Mugo pines, but it may also attack firs, red and Austrian pines, and spruce trees. When looking at a mugo infected with scale, it looks like it has a light layer of snow on the needles. When you look closer, however, you'll see that the white specks on the shrub are actually shells, casing the scale inside.

Source: http://urbanext.illinois.edu/hortanswers/detailproblem.cfm?PathogenID=74

The scale starts off its life being hatched out of the mothers old shell around mid May. The first stage of their lives, they are flat nymphs that are known as crawlers. After hatching, they move to a suitable part of the same tree to hunker down and make their own shell. Some or them may fall off the tree or be taken by wind to another tree, which is usually how the infection spreads.  After finding a needle to call home, they create their own shell and molt inside of it, allowing them to grow for up to three weeks. At this point, the males emerge from their shell as a winged adult, and the females, after mating, lay as much as 40 eggs under their shell. Depending on where you live, they work two hatching seasons into a year. One in mid-May and one in late July. This can make containment difficult.

This picture shows the hard white shells of the adult scale, as well as the new-born nymphs, which apear here as small red dots. Source: http://msue.anr.msu.edu/news/pine_needle_scale_crawlers_should_be_hatching/

As far as treating scale goes, most effective controls have been systemic insecticides. They should be sprayed in June and in August, right as the newborn nymphs are trying to settle in, before creating their shells. Also effective horticultural oil sprays. Dormant oil sprays have proven for the most part ineffective. If you plan on trying these methods, contact your local pesticide dealer and ask for more information.