FUMIGATION OF CITRUS TREES. 65 
The blossoms appear to be much more resistant to the gas than, 
the young leaves or leaf shoots. Trees in which there are blossom 
shoots and tender leaf shoots side by side will have the leaf shoots 
burned back, while the blossoms remain unaffected. This shows that 
the blossoms will stand a much heavier dosage than the tender leaves 
and leaf shoots. 
The young leaf shoots grow so rapidly in certain varieties of trees, 
or even in the same variety of tree in different localities, that during 
the latter part of the blossoming period they almost obliterate the 
blossoms. Although fumigation of these trees will not injure the 
blossoms it will frequently burn back these leaf branches very severely. 
In such cases the grower should not become alarmed by the burning, 
as his trees and future crop of fruit are in no way endangered. Re- 
newed growth will soon take place, while the crop of fruit will be 
exactly as large as if the trees were untreated. 
In conclusion, it might be said that experience in this investigation 
has shown that fumigation can be safely conducted during the 
blossoming period with the dosages at present generally employed 
by fumigators, namely, schedule No. 1. 
FUMIGATION WHILE THE FRUIT IS OF SMALL SIZE. 
The records of several experiments during 1908 in fumigating 
while the fruit was of small size are given in Bulletin 79 of this bureau. 
The results of these experiments demonstrated that heavy dosages 
can not be used while the fruit is small without more or less injury. 
Additional evidence has been secured during the latter part of this 
investigation which has entirely corroborated the earlier experiments. 
Thus it may be stated that the most critical period for conducting 
fumigation is between the time the fruit sets and the time it attains 
a diameter of about an inch. This period occurs during the late 
spring and summer. It is advised not to fumigate during this period, 
which is usually from April to August. Although in some cases an 
orchard may be treated during this period with a light dosage without 
injury, yet the risk is too great to justify such action. It is better to 
wait until the regular season immediately following the month of 
July. 
FUMIGATING LEMONS. 
Throughout this bulletin the recommendations are always for 
citrus trees, which include the orange, the grapefruit (pomelo), and 
the lemon. The acreage of grapefruit is very small. Oranges and 
lemons occur more or less promiscuously throughout the same districts 
where lemons are grown, while frequently an orchard will consist 
partly of each. The orange and grapefruit are about equally sus- 
ceptible to injury from fumigation, while the lemon is much more 
