230 NEW YORK STATE MUSEUM 



Potash wash. — Dr. Smith, in his experiments with the scale in New 

 Jersey, has tested to his entire satisfaction the efficacy of a saturated 

 solution of crude or commercial potash, i. e., potash in a sufficient quan- 

 tity of water to dissolve it, to be used upon trees during their dormancy 

 in the winter season, only. It may be applied either by means of a cloth 

 or stiff brush, or by thorough spraying. The potash eats into or corrodes 

 the scales and kills a large proportion of the insects beneath them. A 

 month later, by which time the scales will • have become riddled or 

 loosened, it should be followed with kerosene emulsion made after the 

 usual formula and diluted to a strength of one part to five parts of water. 

 If these applications are thoroughly made, according to Dr. Smith, " not 

 a single insect need escape." 



Before using any of the above washes, it is recommended to cut back 

 as freely as may be properly done, the infested trees, and burn the cut- 

 tings, as a large part of the scales are to be found on the terminal twigs. 



Summer washes. — Experiments thus far made with applications that 

 may be safely used during the summer, have failed to give a wash that 

 will destroy all thc^ scales ; a small percentage will escape. The two that 

 have given the best results are the summer resin wash and an ordinary 

 diluted kerosene emulsion. With either of these, " by three applications 

 at intervals through the summer, the insects may be kept from increasing 

 to any serious extent." The unattached insects and those in which the 

 scale is in its incipiency will readily be killed, and if it were possible to 

 reach all of them, the entire destruction of the insect would be effected. 

 But this is impracticable. The young are hatching continually during 

 nearly five months of the year, and are to be found at any time during 

 this period in their active stage upon the tree. The number of sprayings 

 that would be required to reach the young before they are protected by 

 their scale, would render this method altogether too laborious and costly 

 to depend upon it for extermination. 



Gas treatment. — The treatment of infested trees with hydrocyanic acid 

 gas, generated wiihin a canvas tent made air-tight through the applica- 

 tion of boiled linseed oil, and fastened closely down over the tree to be 

 treated, has been extensively used in California and with entire success 

 against some of the scale-insects of the western coast. The cost of the 

 tents and the labor involved in their management render it altogether too 

 expensive for general use ; and further, although it has been hitherto 

 claimed that the gas apphed in this manner was absolutely fatal to all 

 animal life, yet late experiments appear to show tliat it may not be en- 



