APPLE INSECTS 163 



makes it of the greatest economic importance. No other scale- 

 insect has ever equaled it in capacity for injury to plants. 



China is believed to be the native home of this pest, and 

 more appropriate common names for it are the ('hinese scale, 

 or the pernicious scale, from the very pat name giv(^n it by 

 Professor Comstock when he described it in 1880. It first 

 became established in America at San Jose, Cal., about 1870, 

 and derived its name therefrom. Previous to its introduction 

 into Eastern nurseries in 1886 or 1887, the scale had gradually 

 spread over most of the states west of the Rocky Mountains. 

 It was not until 1893 that it was discovered in Virginia in the 

 East, but it was soon found to have been already widely spread 

 from these nurseries through thirteen states from New York to 

 Florida. So rapidly has it been spread that important orchard 

 sections in nearly every state and territory, and in Canada 

 and British Columbia, are infested, and it is only a question of 

 time when it will extend over practically all the fruit-growing 

 areas of North America within its climatic range. It occurs 

 also in Hawaii, Chili, Japan and Australia, but stringent legis- 

 lation has thus far prevented its becoming established in Europe. 



The San Jose scale attacks all parts of fruit trees, including 

 the trunk, branches, leaves and fruit, and usually causes reddish 

 discolorations of the bark or skin of fruit (Fig. 169), Clusters 

 of the scales often occur around the stem and blossom end of the 

 fruit, rendering it unsalable, and sometimes giving a pitted ap- 

 pearance. In bad infestations the scales are crowded together 

 and present a grayish, roughened, scurfy deposit on the bark. If 

 scraped, a yellowish liquid results from the mashing of the soft 

 yellow insects beneath the scales. The fruits commonly infested 

 are apple, pear, quince, peach, plum, prune, apricot, nectarine, 

 sweet cherry, currant and gooseberry. Lemons and oranges, 

 except the trifoliate varieties, many shrubs, forest trees and 

 evergreens are practically exempt from attack. 



The fears that shade trees and forests would be ravaged 



