112 
FLORIDA STATE HORTICULTURAL SOCIETY 
an adjoining grove in which all the trees 
were subsequently treated with bluestone 
(copper sulphate). Since it was my de¬ 
sire to ascertain to what extent different 
lime and fertilizer treatments would af¬ 
fect die-back, no bluestone was used on 
the three experimental areas. Neverthe¬ 
less, die-back has now very largely disap¬ 
peared. If bluestone had also been used 
on the experimental trees, it might have 
been inferred that the disappearance of 
die-back was chiefly or wholly due to the 
bluestone. In view of the circumstances, 
however, it is evident that climatic or 
other conditions were responsible for a 
good part of the improvement observed.* 
I do not mean by this that I would not 
advise the use of bluestone as a means 
of combating die-back, for it seems, at 
present, to be the best-known remedy for 
this disease. It must, however, be used 
with care and moderation or trees may be 
injured by it. I say this, notwithstand¬ 
ing that in some cases unusually large 
amounts have been used without injury. 
In the course of my travels for several 
years through the citrus sections of this 
State, covering in all many thousand 
miles and visits made at different times 
of the year, I have not found anyone who 
has been able to tell me positively all of 
the different causes of die-back nor how 
it can always and surely be avoided. Ap¬ 
parently, there may be several causes. At 
any rate, everything which can be done to 
throw light upon any one or more of 
these causes will be of material help to 
the citrus industry. It is for this pur¬ 
pose, among others, that the company 
with which I am connected is conducting 
several experiments in this State with 
citrus fruits on different types of soil. 
We cannot expect that the citrus industry 
of Florida will ever attain its highest and 
fullest development until the mysteries 
connected with the die-back problem have 
*As the discussion following this paper was 
drawing to a close, one of Florida’s authorities 
on citrus diseases, citrus culture, and especially 
on the use of bluestone, disputed the statement 
that die-back had largely disappeared without 
treatment, saying that he had visited the grove 
mentioned and found that this was not the case. 
I thereupon stated that what I said was based 
upon the report of a man also familiar with Flor¬ 
ida and its citrus problems, rather than upon my 
own examination, although I had observed a 
marked general improvement in the grove. Soon 
after the meeting at Miami arrangements were 
made through Professor Newell to have the grove 
carefully examined and reported on by Mr. 
Gumme, county agent and citrus expert of Polk 
County, who reported as follows: 
Section i. No Lime. —Not as heavy growth as 
in Section 2 or 3. Slight indication of frenching. 
Hail has damaged young fruits—also young and 
old wood, causing the wood to split considerably. 
Fruit irregular in quantity. No S-shaped growth 
apparent. No indications of die-back by gum 
pockets or multiple buds. This section could not 
be recorded as having die-back. 
Section 2. Limed Area—Magnesian Lime.— 
Hail damaged fruit and branches as in Section 1. 
Small amount of frenching. Growth in general is 
better than that in Section 1 or 3. S-shaped 
growth is present in almost all trees but there 
are no indications of die-back by gum pockets or 
multiple buds. This section shows vigorous and 
healthy growth. 
Section 3. Limed Area—Non-Magnesian Lime. 
—Die-back present on a few trees which show 
gum pockets, multiple buds, frenching, and brown 
exudation on wood. This condition is not ex¬ 
tensive, although it is marked on a few trees. 
The fruit and wood had been considerably dam¬ 
aged by hail. As in 1 and 2, the damage seems 
to be more marked on the younger wood. 
The Grove Across the Road from the Above 
Three Sections.—This grove has been treated with 
bluestone. No die-back is apparent though a few 
S-shaped branches were noticed. There has evi¬ 
dently been die-back in this grove at some earlier 
period as some of the old wood is stained, but no 
gum pockets or multiple buds were found on the 
younger growth. 
