"Scaling" back on Residential Tree Pests

Jesse Fulbright, MSU Liberty County Extension

Have you ever noticed little, white spots or specks on your spruce or pines trees?  If so, what you are seeing is a very minute, very un-insect-like insect called the pine needle scale.  The pine needle scale is very common on spruce and causes white “specks” that look like bird droppings or paint splatter.  It will also infest Mugo pine, Austrian pine, Scots pine, Ponderosa pine, Douglas-fir, and fir.  Now is the time to start monitoring for the “crawler stage” on those hosts I just listed.

According to a recent Montana Urban Ag Alert, the damage the scale causes is yellowing of needles, premature needle fall, and defoliation with heavy infestations.  They are, after all sap-sucking insects.

The scale spends most of its life under a protective or “armored” shell, which is what we see most often.  The only active stage is the “crawler” stage.  They are mobile for several days and then become stationary.  The crawler stage happens to coincide with the bloom of common lilac.  The crawlers are a purplish color and are about ½ mm long or about the size of a pinhead.

You can check for the crawler stage by putting a white piece of paper underneath some pine needle branches and shaking the vegetation.  If the crawlers are active, they will fall on the piece of paper and will be moving around.

"Crawler" pine needle scale with mature pine needle scale.
Photo courtesy of University of Minnesota Extension.

When the crawlers are active, you can apply foliar sprays or “crawler stage” sprays.  Some of the active ingredients for the crawler sprays include horticultural oils, insecticidal soaps, acephate, permethrin, and cyfluthrin.  Be careful with spruce and oils; they can change the color on Colorado blue spruce trees.  Please note that these are not systemic options; systemics, if choosing this route for control, that have active ingredients such as dinotefuran or imidacloprid, should be applied early in the spring (check the label for timing of application).

As old pine needle scale stay on the needles and don’t often fall off all the time, it can be difficult to tell the difference between old and new populations of scale.  When testing for this, use your fingernail and press down on one of the white shells on the needles.  If a purplish “ooze” comes out or purple eggs are present, then these are new or live populations.  Otherwise, they will be dried out, have an exit hole, and can be scraped off.