SAN JOSE SCALE INVESTIGATIONS, YIIL* 
VV. H: LOWER AND P. J. PARROTT. 
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 . gram of cyanide per cubic foot 
of air space, resulted in practically no injury to apple, cherry, 

*A reprint of Bulletin No. 202. 
