San Jose scale

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San Jose scale

San Jose scale, common name for a scale insect, Aspidiotus perniciosus, introduced from China into San Jose, Calif., c.1870 on nursery stock. The insect has since spread throughout much of the United States and Canada. It is found in the commercial fruit-growing areas throughout the world and is a serious pest of apples, pears, peaches, plums, sweet cherries, gooseberries, and many other trees and shrubs. Only the winged males and young scales are mobile. The young nymphs, or crawlers, move about for a few hours in search of a good feeding spot; then they molt, lose their functional legs and antennae, and secrete a resinous waxy shell, or armor, under which they feed by sucking the sap of the host plant until they become adults. The sedentary female mates and gives birth to several hundred living young while still securely under the protection of the scale, which it never leaves. Two to six generations are produced per year, with an estimated 30 million progeny possible from a single female during one year. Infested trees show a decrease in vigor, take on a gray appearance from the low, conical, overlapping scales, and eventually die if the scale is not controlled. The pest is dispersed by being carried on the bodies of larger insects, on the feet and beaks of birds, by wind, and by shipment of infested nursery stock. The San Jose scale is classified in the phylum Arthropoda, class Insecta, order Homoptera, family Diaspididae.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

San Jose Scale


(Quadraspidiotus perniciosas), an insect of the scale family of the order Homoptera; a quarantine pest.

The adult of the San Jose scale is covered with a bark-colored scutellum. In females the scutellum is round and about 2 mm in diameter; the body is round and lemon yellow in color and has no eyes, antennae, legs, or wings. In males the scutellum is about 1 mm long and 0.6 mm wide; the body is light orange and has one pair of wings, three pairs of legs, and developed eyes and antennae. The San Jose scale is found on all continents. It was first found in the USSR in 1932; its focuses occur in the southern European part of the country, the Caucasus, Middle Asia, and the Far East. It damages more than 200 species of fruit trees, ornamental varieties, and leafy trees. The larvae winter under the scutella on the bark of tree trunks and branches. They turn into females and males in the spring. The female produces 100-300 larvae, or wanderers, which emerge from under the scutellum and adhere to the rough surfaces of the bark, where they remain motionless. There are from one to four generations a year. In sucking the sap from bark, leaves, and fruits, the San Jose scale creates spots and cracks in the bark, kills the bark, and causes the leaves to fall. Severely damaged trees die. Control measures include the use of decontaminated planting stock, the removal of dead bark from trunks and branches, the removal of dry twigs, the thinning of crowns, the destruction of root shoots and severely infested trees, the use of entomophages (ichneumon flies), and the treatment of plants with insecticides.


Popova, A. I. Kaliforniiskaia shchitovka. Moscow-Leningrad, 1962.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.