CITRUS MELANOSE AND ITS CONTROL 29 
EXPERIMENTS FOR MELANOSE CONTROL 
As soon as it was learned that melanose was caused by a fungus 
that speculates in deadwood only, control measures seemed likely 
to be simple. It was then thought that pruning away the dead 
and dying parts of trees would not only be a good general practice 
for invigorating the tree but would also prevent subsequent melanose 
outbreaks for one season at least. With this idea in mind Stevens 
(IS) began pruning experiments in 1913 for melanose control. Up 
to that time melanose was considered by growers generally to be 
a disease that could not be prevented. 
Later the writers conducted spraying experiments for melanose 
control which gave satisfactory results. More recently trial has been 
made of fungicides to be applied in the form of dust, but these have 
not yet proved satisfactory. 
During the first few years of the present investigation the data 
from these control experiments were based on counts of 1,000 fruits 
graded merely as infected or not infected. The counts were made 
while the fruit was still on the tree, and all trees in a plot were in- 
cluded. Whenever feasible only fruit from the lower portions of the 
tree was considered, in order that the data would be from fruits that 
had a good chance to become infected. 
Beginning with the tests of 1922, a study of the actual control of 
melanose more comprehensive than in former years was attempted 
by grading and dividing the fruit into six classes with respect to 
melanose infections. Representative fruits of the various grades 
were photographed and these photographs used as a standard for 
comparison (pi. 4) in these and subsequent counts. Fruit with 
"slight infection" is usually packed in the first grade, and in many 
houses fruit with as much as " medium infection " would be put in 
the first grade. 
The three principal control measures — namely, pruning, dusting, 
and spraying — will be discussed in order. 
PRUNING FOR MELANOSE CONTROL 
Stevens (18, 19) has shown that melanose can be controlled or 
materially reduced by thoroughly pruning out all deadwood. His 
findings have been confirmed in commercial practice by a number of 
growers almost every year, but in the great majority of cases this 
method has not given a satisfactory control. Because of this incon- 
sistency in results obtained by commercial citrus growers it was con- 
sidered advisable to conduct further pruning experiments for mela- 
nose control. 
An old seedling orange grove at Orlando, Fla. (pi. 10, A), with 
more than the average amount 6i deadwood was selected for these 
experiments. In general this grove is about an average one for its 
age, and it is fairly representative of a large percentage of the 
seedling orange groves of the State. Probably 50 per cent of the 
entire orange crop of Florida is at present produced in seedling 
groves. Throughout the pruning experiments only dead and weak- 
ened parts were removed, and the work was done with far more 
care and thoroughness than is likely to be the case in commercial 
work. These experiments were started in January, 1921, when a 
