236 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
The Use of Calcium Cyanide for the Fumigation of Peach 
and Apple Trees for San Jose Scale 
Percent scale dead for different 
periods of treatment 
Amount of 
Date of 
Date 
Kind 
30 
45 
1 
IK 
2 
material used 
treatment 
counted 
of tree 
Min. 
Min. 
Hr. 
Hrs. 
Hrs. 
1 oz. to 25 cu. ft. 11/13/23 
11/23/23 
Peach 
90.5 
94.5 
96.4 
99.3 
83.5 
11/13/23 
11/30/23 
Peach 
96.5 
99.0 
96.5 
99.0 
94.5 
Apple 
100.0 
11/13/23 
12/21/23 
Peach 
100.0 
100.0 
100.0 
98.5 
100.0 
apple 
100.0 
100.0 
1 oz. to 50 cu. ft. 11/16/23 
12/26/23 
Peach 
83.3 
90.0 
94.0 
96.8 
96.8 
Apple 
100.0 
11/16/23 
12/6/23 
Peach 
91.0 
100.0 
100.0 
96.8 
98.5 
Apple 
99.2 
11/16/23 
12/20/23 
Peach 
100.0 
100.0 
99.5 
100.0 
100.0 
Apple 
100.0 
100.0 
100.0 
100.0 
100.0 
1 oz. to 100 cu. 
ft.11/17/23 
11/28/23 
Peach 
98.6 
95.0 
90.5 
91.7 
96.5 
Apple 
96.0 
92.3 
11/17/23 
12/7/23 
Peach 
100.0 
100.0 
94.5 
Apple 
100.0 
99.0 
98.6 
100.0 
12/20/23 
Peach 
100.0 
98.6 
100.0 
100.0 
Apple 
100.0 
100.0 
96.8 
100.0 
100.0 
1 oz. to 
200 cu. ft. 
11/20/23 
11/30/23 
Peach 
70.0 
87.0 
93.9 
70.0 
95.0 
Apple 
97.0 
93.5 
96.0 
11/20/23 
12/20/23 
Peach 
93.5 
97.5 
99.0 
100.0 
100.0 
Apple 
98.0 
100.0 
100.0 
1 oz. to 
400 cu. ft. 
11/24/23 
12/6/23 
Peach 
97.0 
50.0 
97.7 
100.0 
95.5 
Apple 
86.2 
99.0 
100.0 
11/24/23 
12/20/23 
Peach 
82.0 
68.1 
93.7 
100.0 
100.0 
Apple 
54.7 
100.0 • 
100.0 
100.0 
Check. . 12/28/23 Peach Percent Scale dead 62.9 
Apple Percent Scale dead 53.3 
From the results one would naturally draw the conclusion that 
calcium cyanide kills slowly. However, on the first counts made 
wherever it was doubtful whether a scale was alive or dead it was con¬ 
sidered as a live individual. At the time when the last counts were 
made there was no question about the live or dead individuals. They 
were easy to distinguish. This probably explains the difference in the 
percent of kill between the first and last counts. Also the results seem 
to indicate that calcium cyanide used at the rate of 1 oz. to 100 cu. ft. 
will give just as good results as when used at the rate of 1 oz. to 25 cu. ft. 
The thirty minute treatments gave just as good results as the two 
