286 Report oF THE DEPARTMENT OF ENTOMOLOGY OF THE 
all 4483 buds were treated 78 per ect. of which set. The checks 
numbered 4864 of which 85.5 per ct. set, thus making but a slight 
difference in favor of the checks, a difference which might be 
expected from the unusual exposure of the treated buds. 
The experiments with the scale gave somewhat unexpected 
results in that the scales were practically unaffected by winter 
fumigation with the gas at a strength less than .3 gram of 
cyanide per cubic foot of air space. This result has an important 
bearing upon the winter fumigation of nursery stock. To be 
certain of killing the hibernating scales in this latitude the gas 
should be used at the above strength.5 
The spring treatment gave different results. The gas at a 
little more than half the strength (.18 gram) killed the scales in 
every case and did not injure the foliage. 
RECOMMENDATIONS. 
Obviously the first step in combating the San José scale is to 
prevent infestation. Ags the most fruitful source of infestation is 
nursery stock it is plainly of the greatest importance to prevent 
the spread of infested stock. Fumigation with hydrocyanic acid 
gas together with careful inspection and clean cultivation are 
our best safeguards. If stock is to be fumigated too much pains 
cannot be taken to have all conditions right for thorough work. 
Above all else the fumigating house should be gas tight. For 
winter fumigation the gas should be used at a strength of 3 
gram of cyanide. For early spring treatment a strength of .18 
to .2 gram of cyanide will be sufficient to kill the scales. 
An additional safeguard in the nursery is the fumigation of 
bud sticks, scions, etc., especially if such stock has been brought 
from infested localities. The gas at a strength of .22 gram of 
cyanide can be safely used on the common varieties of fruits and 
probably all varieties without danger of injury. 

*For directions for computing the amount of cyanide to use for a given 
number of cubie feet of air space see Bulletin No. 194 of this Station, 
p. 382, 
