Dangerous Character of the Scale 



It is difficult for one to realize fully the dangerous character of 

 the San Jose scale unless he has seen its work. It feeds on the sap of 

 the host plant. The amount of sap that a single individual, or even 

 several hundred individuals could extract could not injure a healthy 

 tree or shrub, but the species multiplies so rapidly, that from a few 

 scattered parents millions of progeny may be produced in a season or 

 two, sufficient to cover completely the bark of parts, or even all, of the 

 tree (PI. I., Figs. 1, 2; and PI. II., Fig. 1.) Most of our insect pests 

 have natural enemies which so restrain their multiplication that they 

 become destructively abundant only now and then ; but those of the 

 San Jose scale are inadequate to its control. A young tree or shrub 

 m.ay be killed by the scale in two or three years ; older trees withstand 

 the attack longer, but sooner or later are likewise destroyed. Young 

 orchards are killed out more quickly than old ones; and where young 

 trees are set in old infested orchards, they also become infested and die 

 before they are old enough to fruit. Wh.erc this insect is present, 

 orchards or otJier plantations containing trees susceptible to its injiiry 

 can only he preserved by spraying. 



The scale does not confine its attack to the bark of the tree, hut 

 infests the leaves and fniit also. The fruit of apple, peach, and pear 

 frequently become as badly infested as the bark. (See PI. III.. Figs. 

 1, 2.) It is comparatively easy to prevent serious injury to the tree 

 by the use of proper measures of control ; but it is very difficult to pre- 

 vent some spotting of the fruit. Scaly fruit is unsightly and unsalable, 

 and does not keep well, and the annual loss in Illinois from this cause 

 is very large, even in orchards which are fairly well sprayed. 



The small size and inconspicuous character of the San Jose scale 

 add very greatly to its economic importance. The liest-trained in- 

 spector can not be depended upon to detect it in every case of slight 

 infestation, and those unfamiliar with it rarely distinguish it until 

 it has done much harm, and has had time to become so widely dis- 

 tributed that its eradication is impossible. 



Life History and Appearance 



The female San Jose scale does not lay eggs, as most insects do, 

 but brings forth living young, which are just visible to the unaided 

 eye as yellow crawling specks. They move about for periods var}ing 

 with the temperature from twelve to forty-eight hours. An experi- 

 ment made in New York by Lowe and Parrott shows that the crawling 

 young may travel at the rate of 2.1 inches an hour as a six-hour aver- 



