BULLETIN 219J , [JANUARY, 191 



Ontario Department of Agriculture 



ONTARIO AGRICULTURAL COLLEGE 



San Jose Scale 



By L. Caesar. 



SUMMARY OF CONTENTS 



The original home of the San Jose Scale is China. It was unwittingly intro- 

 duced into San Jose, California, about 1870. By 1893 or 1894 it had spread all 

 over most of the United States and had even been brought into Ontario. Ship- 

 ments of infested nursery stock were the chief means of its distribution. In Ontario 

 there is believed to be no scale at present north of a line drawn from about Sarnia 

 to Toronto, and more than half of the territory south of this is still free. The 

 scale will probably live and thrive wherever peaches will live and bear some fruit, 

 even though not in a commercial way. It is likely to spread into all such districts, 

 and possibly farther. 



All orchard trees, except sour cherries and usually Kieffer pears, are attacked. 

 Currants and rose bushes, mountain ash and hawthorn, and a few other trees and 

 shrubs are also severely affected. 



The easiest way to identify the scale is to become familiar with the adult female 

 and the immature black stage, and to know that the insect usually causes small, 

 circular, reddish spots on the fruit and a purplish discoloration of the tissues 

 beneath the bark where it feeds. The adult female is almost circular, nearly flat, 

 about 1-16 of an inch in diameter, grayish to ashy brown in color, with usually a 

 small yellowish central area. The immature black stage is found at all seasons 

 of the year and is very small, a mere dot, black, circular, with a nipple in the 

 centre, around which is a depressed ring or groove. 



The first brood of young scales begins to appear about June 20th. There are 

 probably three, or nearly three, full broods a year in Ontario, and young active 

 larvae may be seen up to the severe frosts about the end of October. So prolific is 

 the insect that we may have at least 1,000,000 offspring from a single over-winter- 

 ing female. It is this enormous power of reproduction that causes San Jose scale 

 to be so destructive. 



All parts of a tree above ground are subject to attack. Young trees may be 

 killed in two years, older trees take longer. Orchards not sprayed will, if infested, 

 be destroyed by the insect. 



There are a number of native foes that attack it, but up to the present they 

 are of little importance in Ontario. 



The insect can be readily controlled by a single thorough spraying once a year 

 before tihe buds have burst in spring. Badly infested trees should aIw&js be^sprayed 

 twice the first year. Old apple trees must be well pruned and the rough bark re- 

 moved to secure satisfactory res\ilts. 



