San Jose Scale, Quadraspidiotus perniciosus

Host: This species is known to infest over 60 species of fruit and ornamental trees and shrubs. Pyracantha and cotoneaster are especially susceptible to severe damage. In Oklahoma, it has been recorded from pecan, quince, poinsettia, rubber plant, ivy, Oregon grape, apple, trifoliate orange, plum, pyracantha, pear, and spirea. It occurs mostly on the bark but will infest fruit and occasionally leaves.
Symptoms: Damage is caused when nymphs and adult females pierce plant tissue with their long thread-like mouthparts and suck out plant fluids. The greenish host tissue of shoots and leaves around the scale often turns red. On twigs and small branches the red color extends deeply into the inner bark to the xylem, but the color is not visible at the surface of thick bark. A high population will cause twig and branch dieback, and if some degree of control is not exercised, the entire plant may die. All parts of the host plant except roots may be attacked.' However, the greatest populations occur on twigs and branches where the buildup of scale covers forms a gray crust.
Life Cycle: Partially grown male and female scales overwinter and mature in the spring. After mating, the females produce living young; unlike most scale insects which lay eggs. Feeding and development proceed rapidly, resulting in four or five overlapping generations per year.
Description: The female scale covering is gray, circular, and slightly convex with the exuviae (first molted skin) subcentral and pale or reddish yellow. The exuvia appears as a nipple-like structure surrounded by a circular depression. The male scale is similar in color to the female but is elongate-oval with the exuviae near one end.
Control: Please contact your local county extension office for current information.
Return to Main page