36 INSECT AND FUNGOUS ENEMIES OF THE APPLE. 
of the disease from two or more points on the margin of the original 
spot. 
The leaf-spot disease begins to appear early in the spring soon after 
the first leaves unfold and infections may continue to take place until 
midsummer or somewhat later. A large number of spots may occur 
on a single leaf and in bad cases the trees may become defoliated six 
weeks or two months before the ripening time of the fruit. As a 
result of this premature defoliation the fruit either drops off or re- 
mains small and is of poor quality, the fruit buds are so weakened as 
to decrease the chances for a crop the following year, and the trees 
are materially weakened. 
CAUSE OF THE DISEASE. 
The black-rot fungus known as Sphewropsis malorum Peck is the 
cause of apple leaf-spot, or at least it is the most common cause. 
Other fungi frequently occur on the diseased areas, but they are ap- 
parently secondary, and it has never been definitely proved that any 
of them are capable of producing the leaf-spot described above. 
The black-rot fungus is perhaps the most common fungus that oc- 
curs in pome fruit orchards. In addition to the apple leaf-spot, it is 
the cause of the black-rot of apple, pear, and quince, and produces 
cankers on the trunks and branches of these fruit trees. It also 
erows and fruits on twigs killed by pear-blight and other parasites. 
Spores are produced in great abundance on these dead twigs and it 
is from this source that the leaves most commonly become affected. 
The fungus fruits on the leaves hanging on the trees only sparingly, 
but after the diseased leaves drop to the ground spores are produced 
abundantly. 
TREATMENT. 
Apple leaf-spot is easily controlled by spraying with lime-sulphur 
solution. The treatment for apple scab, as already outlined, will 
effectually prevent this disease, no special treatment being necessary 
where the usual orchard spraying is practiced. During the process 
of pruning affected twigs should be cut off and burned, so as to elimi- 
nate this important source of infection. 
SOOTY FUNGUS AND FLYSPECK. 
Toward the end of the growing season apples may become affected 
with large sooty blotches composed of dark olive-brown matted 
fungus threads. When numerous these blotches give the skin of the 
apple a clouded effect and many fruit growers have learned to call 
the disease “ cloud.” The fungus is superficial, growing on the sur- 
face of the apple, and it does not produce any noticeable diseased con- 
dition of the tissues. However, the sooty or clouded appearance 
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