The pine needle scale is the most well-known armored scale found on conifers in North America. The white, oyster shell-shaped scales can cover needles, creating plant discoloration to needle and limb death. These pests like pines, particularly mugho and Scotch. However, it can infest other firs, Douglas-fir, pines, and spruces.
How Pine Needle Scale Damage Trees
Substantial infestations of pine needle scales eliminate significant amounts of plant juices resulting in discolored needles. From a distance, trees look silvery or frosted. If any outbreaks continue, limbs and twigs could die and will need to be trimmed out.
Life Cycle and Description
This scale stays on the needles of its host and develops shell-shaped, white wax covers. These covers are around 1/8 of an inch when the scales are completely grown.
There is a yellowish spot, the exuvim, on the little end. The male scales are typically slender and smaller. This scale overwinters as deep-red colored eggs are safe under the female's old armor. The eggs hatch in the spring into flat, tiny nymphs known as crawlers.
These crawlers go to new places on the tree to find the right needles on which to feed. These clumsy crawlers usually drop from the trees and could be blown onto trees close by. Once on an appropriate needle, the crawler attaches its mouth and starts to develop new armor. After a couple of weeks, the nymph sheds under the armor and continues to grow in size for about 21 days.
This scale usually is spread by crawlers going from tree to tree. Spread is also swifter when mature trees start to touch branches. Also, scale crawlers could spread with animals or birds which brush or roost against trees with active crawlers. Early discovery will stop the spread and lessen the need for extensive spraying. Using horticultural oil sprays along with insecticides or insecticidal soaps are even more effective.
The pine needle scales are usually killed by the pesticides used for other insect pests. Close monitoring of the parasites and using a pesticide can be successful. It is best to get a professional tree care expert to do the work.