Pine Needle Scale

The following question was sent to the P&PDL diagnosticians here at Purdue University:

Question: I have a pine tree with tiny white things on the needles. What are they and what should I do about them?

Answer: The photo shows pine needle scales. A pine needle scale is an insect that is immobile as an adult and is found on conifers such as pines, spruces, and furs all across the U.S. and Canada. They are small, roughly 1/16 to 1/8-inch long, and live most of their nymph life in a white, oyster-shaped cover that they produce.

A mother scale produces and average of 40 eggs. After they hatch from underneath their mothers scale, the scales are mobile and are called crawlers. The crawlers leave the scale of their mother to find a suitable needle to attach themselves to and extract nutrients from the needle. This can be the same tree or a neighboring tree. During this time they also start to form their own scale cover.

The male scale molts into a winged insect to find a mate. After it leaves its protective covering, the male can only survive for about one day.

Pine needle scales can overwinter as either eggs underneath the mothers scale or as an impregnanted female. Two or three generations of scales may occur in one year.

Since these insects are small, it is very easy to overlook them until heavy infestation occurs. Heavy infestation is visible when the leaves begin to yellow and possibly drop. Repeated heavy infestations can kill branches and sometimes whole trees.

Although biological control methods are ecologically preferrable, insecticides may be used with high infestations. In the case where infestation is severe, it is possible to kill the crawlers during May, June or July when the crawlers are active. Examine the scales to determine their active period before spraying. Use a systematic insect control at this time and follow up the next spring with a dormant oil spray.

Proper timing of application of pesticides is essential if pesticides are necessary. By doing this, you will increase the number of lady beetles and microscopic wasps which are natural enemies of the scales. When using pesticides, read and follow label directions.

-Nathan E. Saxe (June 9, 1998)