Pine needle scales are relatively easy to find and to monitor for crawler activity. Stare at the needles of any urban pine for a minute and you will see white flecks on the needles. These are the scales. You can flip the covers with a pin while looking at them with a hand lens. The females are purple blobs the eggs, if present , will spill out as tiny purple ovals.
There is discrepancy, or really lack of knowledge, regarding pine needle scale life history. According to Armored Scale Insects of Trees and Shrubs (Miller & Davidson 2005) they have one generation per year in far northern states but 2 generations per year from Pennsylvania south. They over winter as eggs in the North but probably overwinter as eggs and as adult females in many places. There are mixed reports.
There is even discrepancy about the species itself. Pine needle scale, Chionaspis pinifoliae, is virtually indistinguishable from pine scale, Chionaspis heterophyllae. The difference, if there is one, is not really important for management since they look the same and have similar life history. Wait until crawlers hatch then use horticultural oil or if necessary something stronger like an insect growth regulator. Check the brand new Nursery and Landscape Pest Control Guide.
A paper from Iowa suggests eggs hatch around 150 GDD. We are well past that now (~360) and am finding adults and eggs right now. Pine needle scale hosts include loblolly pine, scots pine, mugo pine, white pine, and and other conifers including Abies, Picea, Pseudotsuga, and Tsuga.
Every tree has a few so don’t worry about them. Some trees become very infested especially in urban settings where trees may be stressed and natural enemies in low abundance or diversity.