New Youk Agrjcultukal Experiment Station. 287 



As the scale is distributed locally by such agencies as insects, 

 birds and the wind a careful watch should be kept in the orchard 

 for its appearance. Orchard trees that have become infested if 

 considered too valuable to destroy may be treated either by 

 applying a wash or by fumigation with hydrocyanic acid gas. 

 The former method is the only one practical for large trees, such 

 as full-grown apples, and may be employed for smaller trees as 

 well. Crude petroleum is one of the best washes that has been 

 extensively used in the East, although as noted on a subsequent 

 page, a number of others have recently given promising results. 

 Crude petroleum may be used upon apple, pear and cherry trees, 

 in an emulsion with water, in the proportion (40 per ct. of petro- 

 leum) required to kill the scale, without danger of serious injury 

 provided the application is made in early spring. Plums may 

 also be treated with the petroleum-water emulsion but there is 

 more danger of injury. Peaches should not be treated with the 

 emulsion stronger than 25 per ct. petroleum. For summer treat- 

 ment a 25 per ct. emulsion may be used, with reasonable cer- 

 tainty of killing the scales that are reached by the spray. When 

 purchasing crude petroleum it should be remembered that it is 

 safer to use an oil having a specific gravity of 43° than lower. 



The principal advantage of fumigation over treatment with 

 any of the washes is the thoroughness with which the gas does 

 the work. If properly done, probably every scale will be killed 

 by fumigation while it is very difficult, if not impossible, to hit 

 all of them with a spray. The use of the gas in the orchard is 

 practically limited, however, to comparatively small trees be- 

 cause of the expense and difficulty of fumigating large ones. 

 Trees that can be cut back to about twelve or fourteen feet in 

 height by eight or nine feet in diameter can be easily and cheaply 

 fumigated. 



