Sap-Sucking Insects, Gall Formers and Mites
FIELD GUIDE TO INSECTS AND DISEASES OF ARIZONA AND NEW MEXICO FORESTS
Pinyon Needle Scale
Matsucoccus acalyptus (Herbert)

Host:  Piñon

Figure 66. Figure 66. Adult pinyon needle scales appear like small, dark, bean-shaped objects on piñon needles. Piñon needles damaged by pinyon needle scale have a chlorotic (yellow) appearance.

Symptoms/Signs:  Pinyon needle scale is most easily recognized by finding cotton looking egg masses in spring, black bean-shaped nymphs in fall, or emerged adults in April.

Figure 67. Figure 67. Crawler stage of pinyon needle scale.

Biology:  Adults emerge during middle to late April. Adult females are wingless and flightless and males are winged. After mating, females lay clusters of yellow eggs covered with white, cottony webbing around the root collar, undersides of branches, branch crotches, or crevices in rough bark. Sometimes egg masses are found several meters away from piñon trees on a rock or log. Crawlers emerge about 5-6 weeks after eggs are laid. They climb to the ends of branches and settle on the previous year’s new growth. After inserting their piercing sucking mouthparts into a needle, they become immobile. The body becomes covered with wax and turns black in color. This occurs in the Southwest by early June. By October, the larva resembles a small black bean 1.5 mm long. They overwinter in this stage.

Effects:  Infestations can cause needles to yellow and drop. Repeated attacks cause reduced new growth and stunted needles. In severe outbreaks, small trees may be killed outright and larger trees can be predisposed to attack by bark beetles.

Similar Insects and Diseases:  Symptoms of needle scale may look similar to needle cast caused by fungi, but fruiting bodies will be embedded in needles rather than external.

References:  8, 24

Figure 68. Figure 68. Egg masses of pinyon needle scale which are found at or near the base of infected piñon.
Figure 69. Figure 69. Damaged piñon caused by pinyon needle scale.