330 REPORT OF THE DEPARTMENT OF ENTOMOLOGY OF THB 

Caution.—Cyanide of potassium is a deadly poison and hence 
should be properly handled and labeled. When exposed to the 
air for a few hours it absorbs moisture; it should therefore be 
kept in a tight ‘box in a dry place. Hydrocyanic acid gas is also 
very poisonous and hence, when fumigating, the operator should 
be careful that the tent or box has aired for a few minutes before 
he goes inside. | | 
SPRAYING 
A large number of mixtures have been tested with a view to 
ascertaining a satisfactory wash to destroy the scale. At present 
three are considered the most satisfactory here in the East, 
namely, kerosene oil, crude petroleum and whiule-oil soap solution. 
A discussion of kerosene oil is given in the first part of this 
bulletin. 
Crude petroleum.—Crude petroleum can be obtained from any 
dealer in kerosene oil.. The quality that seems to determine its 
value as a safe insecticide is its specific gravity which should not 
be less than 43° (Beaumé oil scale) at 60° F. Oils of lower 
specific gravity have been found to be more dangerous to the 
trees. 
Method of application.—Crude petroleum may be applied pure 
or mixed with water by means of a machine especially designed 
for the purpose. In either case care should be taken not to apply 
too much. The object of the spraying should be to cover every 
part of the tree above ground with as thin a film of oil as 
possible. If it is mixed with water by means of the pump, use 
at least 40 parts of oil to each 60 parts of water making a mix- 
ture containing 40 per ct. oil. 
When to apply—tWate winter or early spring is probably the best 
time to apply the oil but more experiments are needed to deter- 
mine this point. In any case it will be better not to apply it 
after the buds have begun to swell; for although this has been 
done in some cases without apparent injury, in others it has 
ruined the trees. Summer application should be avoided. Care 
should be taken not to put too much on the trees and to make 
