42 



FUMIGATION INVESTIGATIONS IN CALIFORNIA, 



In this experiment, when three-fourths of an ounce of cyanid per 

 100 cubic feet of space was used, hve 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 

 If 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 fiiiit 

 after dosages up to and including the 2|-ounce rate; with 2 J 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 2J ounces to accomplish the same result. 



Table V. — Fumigation for the purple scale, experiment No. 2. 

 [Length of exposure, one hour; height of trees, 11 to 14 feet.] 



a 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 difl'erent dosages on scale infesting the fruit is definitely 

 known. Xo live insects were found infesting the small amount of 

 fruit availal)le. Normal eggs were found after a dosage as high as 

 the If -ounce rate. 



This experiment would lead to the conclusion that for normally 

 shaped orange trees, from 11 to 14 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 Ij ounces per 100 cubic feet will 



