SAN JOSE SCALE INVESTIGATIONS. HI * 



v. H. LOWE AND P. J. FARROTT. 



SUMMARY. 



Spraying experiments with emulsions of crude petroleum and 

 water gave the following results: 



Winter applications of the emulsion containing 25 per ct. of 

 petroleum and higher percentages seriously injured or killed 

 peach trees. European plum trees and apple trees were unin- 

 jured except by 40 per ct. and stronger emulsions. Cherry and 

 pear trees were not injured by either the emulsified or undiluted 

 petroleum. 



Spring applications of the emulsion of the same percentages 

 resulted in serious injury to European plum trees by the undi- 

 luted petroleum, slight injury by the 60 per ct., while the 40 

 per ct. was harmless except to a number of old plum trees which 

 had been somewhat weakened by disease. Peach trees were 

 seriously injured by the 40 per ct. and stronger emulsions. 

 Young cherry and pear trees were uninjured by the diluted and 

 undiluted petroleum. 



Experiments to determine the percentage of petroleum re- 

 quired to kill the hibernating scales resulted in a failure with 

 the 25 per ct., while the 40 per ct. and higher percentages killed 

 the scales in both the winter and spring series. But, as indi- 

 cated above, 40 per ct. emulsion should be used only in spring 

 a short time before the buds begin to swell; and not at any 

 time upon peach trees. 



Fumigation experiments with hydrocyanic acid gas at 

 strengths varying from .18 to .3 gram of cyanide per cubic foot 

 of air space, resulted in practically no injury to apple, cherry, 



•A reprint of Bulletin No. 202. 



