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 safelv 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 hi 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 v§ry 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 



