FLORIDA STATE HORTICULTURAL SOCIETY. 
6l 
and considerable data has been obtain¬ 
ed which shows the superiority of fum¬ 
igation over even the most successful 
spraying, both in regard to cost and 
effectiveness. 
It is the writer’s object to give in 
this paper a concise statement regard¬ 
ing the methods involved in the fumi¬ 
gation of orange groves and the results 
obtained thus far by the experiments 
along this line, looking to the control 
of the white fly. Much more extensive 
experimental work will be conducted 
next winter with the object of testing 
improvements suggested by past ex¬ 
perience, and of reducing the necessary 
cost to a minimum. 
CONDITIONS CONSIDERED NECESSARY FOR 
GOOD RESULTS. 
Isolation of an infested grove is the 
most favorable condition for successful 
control of the white fly by fumigation. 
Next in importance as a favorable con¬ 
dition is concerted action among the 
owners of adjoining groves, in the case 
of groves not sufficiently isolated for 
independent action. Whether or not 
this concerted action will be obtained 
in any particular instance rests with 
those interested in the success of the 
orange growing industry for the prob¬ 
lem of how to accomplish this was 
solved many years ago in California. 
In Florida, Orange county has already 
made a beginning towards the adoption 
of a systematic campaign against the 
\Yhite fly, having organized a Horticul¬ 
tural Commission with powers equivalent 
to those of similar commissions in Califor¬ 
nia. The officials having the matter in 
charge, however, have not felt justi¬ 
fied in attempting active field work on 
a large scale until careful experiments 
shall have determined what course can 
be followed with a certainty of uniform 
results. 
The third condition which strongly 
favors, if it is not absolutely necessary 
for good results, is the absence of the 
white fly food plants other than citrus 
trees. Chinaberry trees including the 
variety called ‘'umbrella” tree cause 
untold injury to orange growing inter¬ 
ests. While all of these trees do not 
become infested each year owing to 
various circumstances which it is unnec¬ 
essary to mention here, it is well 
known that in many localities, espe¬ 
cially in central and northern Florida, 
adult white flies produced by them 
occur in myriads throughout the towns 
in midsummer. Chinaberry and um¬ 
brella trees favor the rapid dissemina¬ 
tion of white flies from centers of in¬ 
fection, also their successful establish¬ 
ment in uninfested localities. They 
seriously interfere with the success of 
fumigation as well as of all other rem¬ 
edial measures by furnishing a favored 
breeding place where the white fly can 
regain its usual abundance in a much 
shorter time than would be the case if 
, 15 
it were entirely dependent upon the 
citrus trees for its food supply. Of the 
other food plants of the white fly, cape 
jessamine and privets should, like the 
chinaberry and umbrella trees, be 
classed as public nuisances in all or¬ 
ange growing sections. ' 
WHEN TO FUMIGATE. 
Fumigation for the white fly should 
be done during December, January 
and February, beginning about two 
weeks after the adults of the last fall 
brood have disappeared, in order that 
