64 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
with these different dosages were about the same. The very voune 
insects were destroyed, but a large proportion of the matured ones 
and eggs escaped. A few trees were then coyered with double tents 
(two tents, one oyer the other) in order to render them tighter and 
twice schedule Xo. 1 was used. An examination of these results a few 
days after treatment showed eradication on some trees, while others 
contained a small percentage of lire adult insects. A 10-acre block 
of trees was then fumigated with double tents (two tents, one oyer 
the other) and twice schedule Xo. 1. An examination of this work 
showed a considerable percentage of live matured insects and eggs. 
From the results of the aforementioned fumigation against the 
mealy bug it is seen that the early stages of this insect are destroyed 
by the use of twice dosage schedule Xo. 1. If a study of the life 
history should reveal that at some certain time they may all be 
found in this early stage of development fumigation might then prove 
of some avail. The failure, however, to secure eradication of the 
mealy-bug in its more mature stages, even where dosages as high as 
three times schedule Xo. 1 were used, indicates that general com- 
mercial fumigation for the mealy bug is impractical. 1 
FUMIGATION DURING THE BLOSSOMING PERIOD. 
The statements by experts on fumigation as to the amount of 
injury resulting from work while the trees are in blossom are very 
conflicting. Some fumigators hold that a very light dosage will 
destroy tender blossoms, while others believe that the blossoms will 
stand a heavy dosage. In order to decide this point, much experi- 
mentation has been carried on and many observations made through- 
out this investigation. To attempt to relate the details of the scores 
of experiments and observations made along this line in all parts of 
southern California would require too much space, so mention will 
be made here only of general results. Fumigation observations by 
the writer have covered the entire period from the time the blossoms 
first appear until the petals drop. In not a single instance during this 
period has any serious injury resulted even though dosages as high as 
1} and 2 times schedule Xo. 1 have sometimes been used. 
Occasionally some blossoms were affected, and dropped off soon 
after the treatment, yet these blossoms were normally weak and 
would have fallen without fumigation. The fumigation merely 
hastened their shedding. Even if a heavy shedding took place 
(which never happens), there would be no cause for alarm, as the 
setting of only a small percentage of the blossoms on a citrus tree is 
necessary to produce a full crop of fruit. 
1 This same conclusion has been reached by Mr. E. O. Essig, horticultural commissioner of Venfura 
County, i See Pomona College, Journal oi Entomology, December, 1909.) 
