Hosts:  Most pines, spruce, Douglas-fir

Figure 73. Closeup of pine needle scale.

Symptoms/Signs:  Damage is especially noticeable on ornamental pine and spruce trees growing along dusty roads. Insects feed by sucking sap from needles, causing the needles to yellow and eventually drop.

Biology:  The pine needle scale has two generations per year. The 3.5 mm long mature female scales are most conspicuous. They are almost pure white, slender at the front with a wider rear end. Males are smaller and slender and rarely seen. Twenty to 30 eggs are laid in the fall and winter beneath the dead female scale. Eggs hatch in May and the nymphs, or “crawlers”, move to new green needles to feed. Nymphs mature by early July, adults mate, and new clusters of eggs are laid. Scales of this second generation mature by fall and lay the overwintering eggs.

Figure 74. Ponderosa pine branch with pine needle scale.

Effects:  Heavy infestations over several years can kill young trees and severely weaken larger trees, predisposing them to attack by other pests.

Similar Insects and Diseases:  Damage may be similar to that caused by other agents that discolor needles such as black pineleaf scale, pine needle casts, winter desiccation, drought, and aphids. If scales are present, diagnosis is assured.

References:  8, 33