Origin:
Despite its common name this is a native insect in North America, and is found in many fruit growing states.
Biology:
This scale attacks a variety of deciduous trees and vines, and occasionally may be found on some evergreen shrubs. It is a pest on stone fruits such as peach and apricot as well as on grapes, and the honeydew drippings and resultant sooty mold can disfigure the fruit and make it unmarketable. Normally a single generation per year in cooler climates, and 1 or 2 generations in warmer regions. Females begin laying eggs in the spring with the first instar crawlers emerging from mid-spring into early summer. The mobile crawlers then move to fresh shoots and leaves and feed there. Once they molt to the second instar they return to stems of 1 to 3 year old wood and become sessile, forming the wax scale over themselves and never moving again. Adult females overwinter.
Identification:
Mature females are brown to reddish-brown and quite rounded or convex. Younger females are more flattened and have a pale colored stripe across the top. The adult scales are very large, up to 0.4 inch across. Males are not known, as females reproduce parthenogenetically.
Characteristicts Important to Control:
The scale itself rarely causes much damage to the host plants, but the presence of honeydew and sooty mold may be objectionable or cause fruit to be unusable. Controlling ant populations will encourage the presence of the many parasitic and predatory insects that feed on the scales. A dormant oil application in the winter can kill overwintering females, and an application of an insecticide timed to when the crawlers are emerging will effectively kill the first generation. This may be done with a labeled material including oils, botanical sprays, or synthetic insecticides.
