FLORIDA STATE HORTICULTURAL SOCIETY. 
89 
of the groves in one locality was con¬ 
ducted to see if the disease was limited 
to any particular soil or method of treat¬ 
ment. The disease was found to be pres¬ 
ent upon all soils in that section. The 
soils were mostly hammock or high pine 
land. The disease was equally present 
in groves that had received clean culture, 
in those that had no cultivation, and in 
those that had been more or less culti¬ 
vated. The disease was equally preva¬ 
lent in a shedded grove and in one that 
was not shedded, the two being located 
side by side. 
In the shedded grove, where sections 
of the roof had been removed, so as to 
expose to direct sunlight portions of 
trees that were previously shedded, the 
spotting was found to be more plentiful. 
Very few trees under three to four 
years of age were diseased. In the ma¬ 
jority of cases, the disease was most pre¬ 
valent upon trees that had recently borne 
a heavy crop of fruit. This would sug¬ 
gest a relation of the disease to the weak¬ 
ened condition of these trees. 
The spotting was found to be worst in 
the upper branches of the trees. When 
present on the lower branches it is usually 
thinly scattered. It often happens that a 
particular branch or twig may have the 
majority of its leaves affected, whereas 
the leaves of neighboring branches are 
perfectly healthy. This is particularly 
noticeable in trees that are only slightly 
diseased. Since these branches seem 
equally strong, there is presumptive evi¬ 
dence that the origin of the disease is 
within the plant, or in the soil. 
The disease is not confined to any par¬ 
ticular variety of citrus. It is most evi¬ 
dent on the grape fruit, on account of 
the larger size and deeper color of its 
leaves; and it is least evident upon the 
tangerine, on account of the smallness of 
the leaves. The disease is equally harm¬ 
ful to all the varieties of citrus which 
may be affected by it. 
SYMPTOMS. 
The symptoms of the Yellow Spotting 
of citrus are confined to the leaves. A 
spotting of the fruit resembling the spot¬ 
ting on the leaves, has been noticed in 
only one case. 
There are many variations in the gross 
appearance of the spots, thus making it 
difficult to give an exact description of 
them. These variations are evidently due 
to the different reactions of the leaf-tissue 
to the disease stimulus. The typical spots 
on the leaves are yellowish to golden-col¬ 
ored areas, a fraction of an inch or more 
in diameter. They usually occur be¬ 
tween the main veins and extend through 
the substance of the leaf. The areas dif¬ 
fer in appearance on the upper and un¬ 
der surfaces. On the upper surface, the 
yellowish or golden color is more notice¬ 
able ; the central portion of the area is 
often darker in color than the margin. 
It often presents a shiny, dark-brown ap¬ 
pearance. The discolored area is not 
raised above the surrounding surface of 
the leaf. The surface of the spot on the 
lower side of the leaf is often rough and 
projecting. It usually has a dull, greasy 
look, and a yellowish-brown or olive-green 
color. The surface in old spots may be¬ 
come dark colored and melanose-like. 
A cross-section of a healthy orange 
leaf when studied under the microscope, 
shows the leaf to be made up of layers 
of cells, Fig. i. The upper surface of 
