LEAKAGE OF GAS IN SMALL TREES. 



43 



destroy the purple scale in all its stages on the leaves and wood. If 

 the tree contain fruit infested with this scale it will be necessary to 

 slightly increase the dosage. The exact amount of this increase can 

 not be stated with accuracy at this time, owing to the fact that in the 

 single experiment performed very little infested fruit from which 

 data might be secured was available. 



Table VI. — Fumigation for the purple scale, experiment No. S. 

 [Length of exposure, one and one-half hours; size of trees mostly 7 to 10 feet; occasionally one 11 or 12 feet.] 



a No material for examination. 



In this experiment live insects were found on the branches and 

 leaves in the cases where three-fourths ounce and 1-ounce dosages were 

 employed. Normal eggs were found up to and including the l|-ounce 

 rate, but were destroyed by dosages exceeding this. As in the case of 

 experiment No. 2, so little scaly fruit was available at that time that 

 we are inclined to consider the results in this part of the test as yet 

 incomplete. 



THE LEAKAGE OF GAS IN FUMIGATING SMALL TREES. 



When the results of experiment No. 3 are compared with those of 

 experiment No. 2 we are at first led to believe that an error has been 

 made. In experiment No. 2 it was found that the l|-ounce dosage 

 rate destroyed all insects and eggs on the leaves and branches, whereas 

 in this experiment it required one-half ounce more cyanid per 100 

 cubic feet, or a 2-ounce dosage rate, to accomplish the same result. 

 Since the period of exposure was thirty minutes longer than that of 

 experiment No. 2, we would naturally expect that the results accom- 

 plished would be as good or better, all other conditions being the 

 same. The apparatus and chemicals employed were identical in both 

 cases; and the conditions under which the fumigation was conducted 

 were practically the same. There was, however, one difference: The 

 trees involved in the one and one-half hour fumigation were much 

 smaller than those of the one-hour test. This fact accounts for the 



