October ,’24] 
CAMPBELL: CALCIUM CYANIDE FOR WIREWORMS 
563 
June, 1923, 10-inch pots of soil being used, followed, in- August, by 
field tests at Toppenish, Wash. 2 
In the pot experiments, various types of soil were used, as well as 
moist, dry, loose, and packed soil, and the relative locations of the 
cyanide and wireworms were also varied. A summary of all of the ex¬ 
periments show the following: 3 
Table I— Showing Percentage of Wireworms Killed by Different Amounts 
of Calcium Cyanide Dust per Acre in Pot Experiments at Alhambra, 
California, in 1923 
Pounds 
per acre 
Maximum 
Per cent killed 
Minimum 
Average 
Number of 
experiment 
Total number 
of worms used 
400 
100 
70 
92 
9 
90 
350 
100 
30 
80 
12 
120 
300 
100 
30 
71 
12 
120 
250 
90 
30 
65 
12 
120 
200 
100 
10 
50 
13 
130 
150 
90 
0 
40 
11 
110 
Control 4 
10 
0 
1 
9 
90 
Although nearly a hundred experiments were performed, they were 
not considered sufficient to explain entirely the variations in results. 
An analysis of the experiments, however, suggests the following factors 
as having a bearing on the success or failure resulting in several cases: 
(1) Depth of Cyanide. Following shallow applications, there re¬ 
mained in the pots a considerable percentage of live worms, nearly all of 
which, except in the case of light dosages, were several inches below the 
cyanide. It was therefore concluded from the rather meager evidence 
that the killing of few wireworms below the cyanide could be expected. 
(2) Mechanical Condition of the Soil. In experiments where the 
soil was left very loose, the killing in most cases was low, probably 
owing to the fact that the gas was allowed to escape too rapidly. Where 
the soil was packed hard, also, the killing was low, owing to the diffi¬ 
culty with which the gas penetrates soils in this condition. 
(3) Activity of the Wireworms. As the experiments continued 
into the fall and the wireworms became less active, results showed 
■ 
2 The experiments at Toppenish were carried on under the writer’s direction by Mr. 
John N. Stone. 
3 In these experiments calcium cyanide dust was used, while for field work the 
granular form was used. 
4 Of the 90 worms used in the controls, 86 were recovered, 85 alive and 1 dead. 
However, in none of the experiments were missing worms considered as having been 
killed. In computing the percentage of killing, only the dead worms actually re¬ 
covered were used. 
