ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



prisingly short time under favorable conditions, as the progeny of 

 a single female may amount to several million insects in one season. 

 Laws in some States prohibit the marketing of infested fruit except 

 for the purpose of making byproducts. 



The San Jose scale is so named because it was first found at San 

 Jose, Calif. It is native to China and was evidently brought into 

 California with plants of some kind about 1870. It has since been 

 widely distributed on nurs- 

 ery stock and by other 

 means, and at present oc- 

 curs in practically all of the 

 fruit districts in the United 

 States. It does more harm 

 to apple and pear trees than 

 to other fruits, but is at 

 times a serious pest of sweet 

 cherry, peach, and prime 

 trees. It also attacks other 

 deciduous fruit trees, nuts, 

 and berries, as well as many 

 kinds of shade trees and 

 ornamental shrubs, among 

 them the mountain ash, 

 currant, dogwood, elm, 

 gooseberry, hawthorn, lilac, 

 linden, poplar, snowberry, 

 willow, and the ornamental 

 flowering varieties of fruit 

 trees. Many of these plants 

 or trees grow in the gardens 

 or about the houses in fruit- 

 growing districts, and un- 

 less they are regularly in- 

 spected and are sprayed, if 

 infested, they are very 

 likely to be troublesome 

 centers of infestation for 

 nearby orchards. 



LIFE HISTORY 



The San Jose scale re- 

 mains in one place during 

 most of its life. In the fall 

 practically all stages may 

 be found on the trees, but 

 only those that are about half grown survive the winter, and in severe 

 winters many of these succumb. Temperatures of — 15° to —20° F. 

 cause a mortality of approximately two thirds of the half-grown 

 scales, and 90 percent or more are killed if the temperature gets as 

 low as —25° or —30°. In the spring the scales that have survived 

 continue their growth and mature in Mav or June. The males develop 

 wings and are active, although they do little flying. The females 

 have no wings, remaining where they have developed and producing 



167469°— 33 2 



Figure 7.— Bark encrusted with the San Jose scale, 

 times natural size. 



