26° FARMERS’ BULLETIN 650. 
been indicated, the petroleum oils are at times the cause of injury 
to twigs and fruit buds, in extreme cases killing the trees. It is a 
question of judgment whether, under conditions of severe scale 
infestation, the petroleum oils or the sulphur solutions should be 
used. The petroleum oils, on the whole, are more effective and the 
danger of injury from them is less to pome than to stone fruits. 
The practicability of making miscible oils at home has been investi- 
gated by Prof. C. L. Penny, and he has shown it to be entirely feasible, 
as detailed in the publications cited below.' 
Fic. 17 —Gasoline power spraying outfit for use in large orchards. (Original.) 
SOAP WASHES. 
Practically the only soap wash which has come into extended use 
against the San Jose scale is that made from fish oil. Fish-oil soap 
is used mostly on dormant trees, being employed at the rate of 2 
pounds to the gallon of water. 
A potash fish-oil soap is preferable and should contain not more than 
30 per cent of water. Soda soaps, while perhaps cheaper, will be 
1 Penny. Charles L. Petroleum emulsions. Del. Agr. Col. Expt. Sta., Bul. 75, 39 p., June 18, 1906. 
Penny, Charles L. Miscible oils: How to make them. Penn. State Col., Bul. 86, 20 p., fig., March, 1908. 
