Get Printable PDF Version

Pine needle scales. Note adult scale with an egg appearing from under the cover (pink) and the settled crawler in the upper left.

Pine Needle Scale

Pine needle scale settled crawlers (amber), and crawlers (pink).

Species:

Chionaspis pinifoliae (Fitch) is the correct species and most common in Ohio, but sometimes C. heterophyllae Cooley is found which looks much like the former. The life cycles are considered to be very similar.


Distribution: Most of the United States and Canada.


Hosts: Prefers pines, especially Scotch and mugho; can infest spruces, firs and Douglas-fir.


Damage:

Heavy infestations of pine needle scales remove considerable amounts of plant juices resulting in yellowed needles. From a distance, trees appear frosted or silvery. These needles often drop early or die and turn brown. If heavy infestations are allowed to continue, whole twigs and branches will die.


Description and Life Cycle:

This scale settles on the needles of its host and forms white, oyster shell-shaped wax covers. These covers or armor are about 1/16 to 1/8-inch long when the scales are fully grown and there is a yellowish spot, the exuvium, on the small end. The male scales are usually smaller and more slender. This scale overwinters as deep reddish colored eggs protected under the females' old armor. The eggs hatch in mid-May into tiny, flat nymphs called crawlers. These crawlers creep to new places on the tree in order to find suitable needles on which to feed. These clumsy crawlers often fall from the trees and may be blown onto nearby trees. Once settled on a suitable needle, the crawler inserts its hair-like mouthparts, and begins to form the new armor. After a couple of weeks, the nymph molts under the armor and continues to increase in size for about three weeks. By this time, male scales are smaller and more slender than the females. The males molt into a prepupa for a week before emerging as winged adults. The females, however, molt into wingless nymph-like adults. After mating, the females continue to grow for a couple of weeks before laying eggs under the armor. Females produce an average of 40 eggs.

Two generations of this scale normally occur but longer summers may allow for three generations. The overwintering eggs hatch in mid-May and the summer produced eggs hatch in late July. The first spring hatching generally occurs over a 7-10 day period. Unfortunately, the second generation of eggs may hatch over a period of two to three weeks.


Control Hints:

This scale normally is spread by crawlers being blown from tree to tree though recent research has suggested that the crawlers may hitch a ride on birds and mammals travelling through the plantation. Spread is most rapid when mature Christmas trees begin to touch branches. Early detection will prohibit spread and reduce the need for spraying entire plantations. Remove mature trees from forest land surrounding a plantation because these serve as infestation sources.

Option 1: Biological Control - Encourage Natural Predators and Parasites - The twice-stabbed lady beetle (jet black with two red spots), another tiny black lady beetle and several parasitic wasps seem to control the pine needle scale in forest stands. However, these biological controls are usually killed by the pesticides used in Christmas tree plantations for the control of other insect pests. Apply pesticides only when necessary and target the crawlers as closely as possible so as to conserve the natural enemies of this scale.

Option 2: Chemical Control - Dormant Oil Sprays - Since these scales overwinter as eggs, dormant oil sprays (3-5%) applied in late fall and early spring have not been very successful.

Option 3: Chemical Control - Horticultural Oil and Soap Sprays - Horticultural oil (1.5-2%) and insecticidal soaps have been very effective in controlling the newly settled crawlers. Make the applications after the eggs have hatched but before the settled nymphs have begun to form new white waxy coverings.

Option 4: Chemical Control - Standard Insecticide Sprays - Registered insecticides are most effective if applied against the newly settled crawlers. Make applications after the eggs have hatched but before the formation of the new waxy coverings. The first generation is the most desirable to control because most of the crawlers emerge over a short period of time. If the second generation is targeted, two sprays may be needed in order to catch late emerging crawlers.