302 NEW YOKE STATE MUSEUM 



back as freely as may be properly done, the infested trees, and 

 burn the cuttings, as a large part of the scales are to be found on 

 tlie 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 the 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 unat- 

 tached 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 hydro- 

 cyanic acid gas, generated within a canvas tent made air-tight 

 through the application of boiled linseed oil, and fastened closely 

 down over the tree to be treated, has been extensively used in Cali- 

 fornia 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 applied in this manner was absolutely fatal to all animal life, yet, 

 late experiments appear to show that it may not be entirely depended 

 upon for the complete destruction of the San Jose scale when infest- 

 ing orchards. According to Mr, Howard, an orchard in Charlottes- 

 ville, Va., which had been treated with the gas in March last, under 

 the skilled supervision of Mr. Coquillett, — although " the operation 

 was as thorough as it could be made, a few of the insects survived 

 the treatment, as was shown by the receipt of living specimens late 

 in the fall from Dr. Hedges." {Insect Life, vii, p. 286.)* 



*Mr. Howard has since made personal examination of this orchard, and has 

 found the gas treatment inefficacious. The trees are again badly infested, while 

 one result of the fumigating has been to seriously injure the trees by causing the 

 blackening and cracking of the bark. 



