THE SAN JOSE SCALE 



{Aspidiotus perniciosvs Comstock) 



By PRESSLEY A. GLENN 



The San Jose scale is capable of doing more injury in Illinois 

 to fruit-trees and many other valuable trees and shrubs than any other 

 insect in the state, and as no general article on the species has ever 

 been printed in the State Entomologist's report or in the Bulletin of 

 the Illinois Agricultural Experiment Station, it is believed that a com- 

 prehensive discussion of the subject, brought down to date, will have 

 a considerable practical value. 



This insect is so inconspicuous that it may easily be overlooked; 

 and its power of multiplication is so great that, in a comparatively 

 short time, it may overspread the trunk, limbs, twigs, leaves, and even 

 the fruit, of the trees or shrubs which it infests, either killing the plants 

 outright, or so injuring them that they become worthless. (See PI. I., 

 Figs. 1, 2; PI. II., Fig.. 1 ; and PI. III., Figs. 1, 2.) It is primarily an 

 orchard pest, and is most important in large commercial orchard dis- 

 tricts; but it is also very injurious in parks and private grounds, and 

 on lawns in cities and towns. Its control is much more difficult in 

 towns than in orchard districts, because in the former the values in- 

 volved in each case are commonly too small to make it seem worth 

 while for the property owner to go to the trouble and expense of 

 getting the information and equipment necessary for its destruction; 

 while in the latter the interests involved warrant the expenditure of 

 money and time necessary to its effective control. 



Origin and Distribution 



The San Jose scale is a native of China, and it was probably 

 introduced into the United States direct from that country about 1870, 

 on trees imported by James Lick, of San Jose, Cal., for plant- 

 ing on his private grounds. By 1873 it had become destructively 

 abundant in orchards surrounding the premsies of Mr. Lick, and it 

 soon became known as the San Jose scale. In 1893 it was discovered 

 at Charlottesville, Va., and by 1895 it had been found at various 

 points in thirteen of the eastern and central states. In nearly every 

 instance the infestation was traced directly or indirectly to one or the 

 other of two large nurseries in New Jersey, from which it had been 

 sent out on infested stock. 



