Crabapple, flowering (Malus)-San Jose scale

Quadraspidiotus perniciosus

Pest description and damage San Jose scale is a pest of many ornamental and wild trees in the PNW, particularly in hot, dry climates. San Jose scale can be differentiated from other scale insects by the hard, gray to black, and cone-shaped scale covering the insect. The scale is about 0.06 inch in diameter, and has a tiny white knob in the center with a series of grooves or rings around it. Twigs with infested bark are roughened, rather than smooth, and twig death may occur. Often there is a purple halo on the bark around the scale. At high population densities, fruit is also infested and displays these dark halos about the scales. Crawlers are flat and yellow and common in June and again in August to September.

For biology, life history, monitoring and management


See "Scale insect" in:

Management-chemical control

See Table 1 in:

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