102 
FLORIDA STATE HORTICULTURAL SOCIETY 
acid gas under tents against the insects 
and the conditions under which it may 
be applied. Since Prof. C. W. Wood- 
worth, of the California Experiment 
Station, has made a study of fumigation 
questions with special reference to citrus 
trees, and had a year’s leave of absence 
from California to study in the East, we 
succeeded in securing his services for a 
month to help introduce the process into 
Florida. 
We experimented with various pat¬ 
terns of tents, hoop tents, sheet tents 
and box tents, for small and medium 
trees, and bell tents for very large trees. 
We developed a new form of derrick for 
handling the bell tents that has some 
good points, and may prove to be su¬ 
perior to the California patterns. 
Besides carrying on investigations re¬ 
lating to the life history and physiology 
of the white fly, our chief aim was to de¬ 
termine the susceptibility of the insect 
to poisoning with hydrocyanic acid gas, 
and the effect of the gas upon trees fu¬ 
migated under different conditions. 
Without going into details, we found 
that the fly yielded very readily to the 
gas, much more readily than the com¬ 
mon scales, and that they were practi¬ 
cally exterminated with lighter charges 
than are used in common California 
practice. In looking over thousands of 
leaves upon many different trees that 
had been fumigated two or three weeks 
previously, we were able to find but a 
single insect living. Many of these sin¬ 
gle leaves had hundreds of living insects 
on them when they were fumigated. We 
feel sure that an infested grove, if thor¬ 
oughly fumigated once, would need no 
further attention for two or three years 
unless insects came in from the outside. 
The fumigating was done at night, in 
cloudy weather, in bright sunshine, and 
at varying periods of the day. The be¬ 
havior of the gas seems to be somewhat 
capricious, but no great permanent in¬ 
jury was done under any circumstances. 
Sometimes all the foliage would drop 
from the trees, sometimes part of it, and 
sometimes almost none of it. Fumigat¬ 
ing done with the sun at high merid¬ 
ian seemed most dangerous to foliage 
and crop, but results were sometimes 
contradictory. All trees are reported 
to be in good condition at the present 
time, but some with extra full crop and 
some with light crops, some with mark¬ 
ed difference in crop in different quar¬ 
ters of the same tree. The general 
bearings of the experiments seem¬ 
ed to indicate that the dropping of 
the foliage from trees in Florida did not 
injure them as in California; that fumi¬ 
gation with the winter brood of insects 
can begin in the winter and continue un¬ 
til the middle of February; that it can 
be carried on safely and effectively from 
4 o’clock p. m. until 9 o’clock a. m. the 
following morning, or throughout the 
day, if cloudy and not windy or wet. The 
variation in crop on different sides of the 
same tree is possibly explained by sup¬ 
posing the wind to cause variation in the 
density of gas in different parts of the 
tent. 
It is not wise for one to undertake fu¬ 
migating work on a large scale without 
the assistance of some one who has had 
practical work in the field. It will be 
sometime before such work can be gen¬ 
erally practiced in Florida, but we ex¬ 
pect to see thousands of tents in use in¬ 
side of three of four years. In short we 
expect to see a large part of our great 
annual loss eventually saved. 
