54 FUMIGATION FOR THE CITRUS WHITE ELY. 
varieties. Grapefruits are slightly susceptible to this injury, while 
tangerines appear not at all susceptible, although considerable shed- 
ding of the fruit occurred in one instance when the recommended 
dosage was doubled. 
SUGGESTIONS FOR THE FUMIGATION OF SMALL TREES. 
IN THE GROVE. 
In discussing the style of fumigating tents desirable for use against 
the white fly the author has referred to the advantages of the use of 
box covers for small trees. In many cases complete defoliation of 
the trees during the winter months would be the best method of 
checking the pest, but fumigation is preferable under most circum- 
stances. The dosage with box covers will depend upon the tightness 
of the cloth used. It has been recommended that the cloth be made 
as nearly air-tight as possible by means of paint, or that air-tight 
oilcloth be used. The rate of dosage can be readily determined by 
means of a series of tests, beginning with 1 ounce of potassium 
cyanid for each 170 cubic feet of space (0.00588 ounce per cubic 
foot) and decreasing the number of cubic feet per ounce 10 feet for 
each experiment until the results are satisfactory and uniform. Xo 
experiments have thus far been conducted by the author along these 
lines, but it is expected that in the course of the investigations of 
the white fly now under way in Florida this phase of white fly con- 
trol will be given consideration. 
IN THE NURSERY. 
Several square yards, including many trees, can be covered in the 
nursery by a single tent. If the cloth is unpainted, the dosage for a 
first trial can be calculated by first determining the ratio of the leak- 
age surface to the cubic contents and referring to Table VIII in this 
bulletin, where the recommended rate of dosage will be found for the 
various ratios. The results of the preliminary tests should be care- 
fully observed before fumigating on a large scale, in order that the 
rate of dosage may be adjusted to suit the tightness of the cloth used 
as a cover. 
NURSERY STOCK FOR SHIPMENT. 
Prof. H. A. Gossard, formerly of the Florida experiment station, 
has determined that in an air-tight fumigatorium 1 ounce of potas- 
sium cyanid for each 170 cubic feet of space/' is sufficient to destroy all 
« "One gram to 6 cubic feet of space," lie reports, "seemed sufficient to kill every- 
thing, but to make the dose more certain 1 gram to 5f cubic feet was adopted as the 
standard dose and has been repeatedly tried, always giving the uniform resull of kill- 
ing all larvae pupa'' and adults." Bui. 67, Fla. Exp. Sta., p. 652. One ounce is 
equal to 28.35 grams, from which it is calculated thai 1 gram for <i cubic feet of space 
i- equal to 1 ounce for 170 cubic feet and 1 gram for 5} cubic feet is equal to 1 ounce 
for 163 cubic feet. 
