42 
FUMIGATION INVESTIGATIONS IX CALIFORNIA. 
In this experiment, when three-fourths of an ounce of cvanid per 
100 cubic feet of space was used, live adult females were found on 
the leaves and branches, but the insects were killed by all greater 
dosages; normal eggs were found after the use of a dosage as high as 
1} ounces per 100 cubic feet. Live insects were found on the fruit 
after both the three-fourths-ounce and 1 -ounce tests, but were de- 
stroyed by the heavier dosages; normal eggs were found on the fruit 
after dosages up to and including the 2J-ounce rate: with 2$ ounces 
per 100 cubic feet, all were apparently destroyed. 
This experiment indicates that for normally shaped orange trees, 
from 11 to 14 feet in height, situated in a region with conditions 
comparable to those at Orange, and exposed to the gas for thirty 
minutes, a dosage of about 2 ounces per 100 cubic feet is required 
for eradication of the purple scale from the leaves and branches. If 
the trees contain fruit infested with scale, it is necessary to increase 
the dosage rate to 2\ ounces to accomplish the same result. 
Table V. — Fumigation for the purple scale, experirm nt No. 
[Length of exposure, one hour; height of trees, 11 to 14 feet.] 
Number 
of trees 
treated. 
Cvanid 
per 100 
cubic feet 
of space. 
On leaves and branches. 
On fruit. 
Insects 
alive, 
approxi- 
mately. 
Eggs normal, 
approximately. 
Insects 
alive, 
approxi- 
mately. 
Eggs normal. 
4 
4 
4 
4 
4 
4 
4 
4 
Ounces. 
1 
U 
IV 
lj 
2 
2 l 
2£ 
ooo ooooo 
1-5 percent. 
1 percent or less. 
2 doubtful cases. 










00 
Many instances. 
Several instances. 
(°) 
One doubtful 
Few instances of normal eggs on 
one fruit. 
No instances of normal i e 
CO 
( a ) 
n No infested fruit on these trees. 
With an exposure of one hour all insects were destroyed on the 
leaves and branches at a three-fourths ounce dosage rate. All eggs 
were destroyed at the H-ounce dosage rate. Since very few oranges 
infested with scale were found on the trees used in this experiment, it 
is considered that further investigation will be necessary before the 
effect of different dosages on scale infesting the fruit is definitely 
known. Xo live insects Avere found infesting the small amount of 
fruit available. Normal eggs were found after a dosage as high as 
the 1 v-onnce rate. 
This experiment would lead to the conclusion that for normally 
shaped orange trees, from 11 to 1 i feet in height, exposed to the gas 
for one hour, and situated in a region with conditions comparable to 
those at Orange, a dosage rate of 1J ounces per 100 cubic feet will 
