100 



In some of the eastern states, however, hymenopterous parasites 

 of the San Jose scale have been notably more abundant during the last 

 two or three years than formerly, and in some localities the percentage 

 of parasitism has been very high. (See PI. IV.) Apparently 

 however, this high percentage has not remained permanent. In some 

 localities, at least, where parasites were very abundant for one year, 

 scarcely any could be found the next, tho the scale itself continued to 

 be destructively numerous. We may confidently expect, however, that 

 as the number of species of parasites which attack it increases, and as 

 they become better adapted to it as a host, they will prove more and 

 more effective ; and they may indeed come to control it in time as 

 thoroly as they now control our native species. 



To learn whether the eastern parasites of the scale are present 

 in Illinois, twigs bearing it were collected in the fall of 1913 from 

 thirty localities in central and southern Illinois, and kept in breeding- 

 cages. From about half of them no parasites were secured; from the 

 other half a small number were obtained, all of one species (Aphelimis 

 fuscipennis) . 



This is one of the species found in the East, but it is not the most 

 abundant there ; and an attempt has been made this season to introduce 

 parasites from the eastern states into Illinois. This has been at least 

 partially successful, but only enough scales thus parasitized have been 

 found to show that the transfer was actually made. 



From San Jose scales collected in northern Illinois last fall (1914), 

 large numbers of parasites emerged, examples of which were identified 

 by Dr. L. O. Howard as belonging to the following species : Perissop- 

 terus pulchellus How., Aphelimis diaspidis How., Micropterys sp., 

 Signiphora nigrita Ashm., Prospaltella aurantii How., and Prospaltella 

 perniciosi Tower. This list includes all the more important species 

 found in the East. The first three were not plentiful enough to be im- 

 portant, but the last three were abundant, and may be of practical 

 use if we can secure a more uniform distribution of them thruout the 

 state. For the present, however, spraying is our only means of defense. 



Preventive Measures. — To prevent the dissemination of the San 

 Jose scale by way of the nursery trade, all states now require an inspec- 

 tion of nursery stock, and prohibit the shipment of such stock unless 

 accompanied by an inspection certificate. All Illinois nurseries are 

 inspected each year; and those which are at all likely to be infested 

 by the San Jose scale are inspected at least twice annually. All nursery 

 stock found infested in them is immediately destroyed, and all stock 

 which, on account of its proximity to infested trees and shrubs, is at 



