PEACH SCAB AND ITS CONTROL. 43 
do the earlier infections of twigs and leaves. No other source of 
infection is known to be available until sporulation occurs on lesions 
of the current year's production. In northern Georgia this does not 
usually take place to any considerable degree until early June. 
Secondary. — Conidia from lesions of the current year's production 
constitute the source of secondary infection. On account of the 
long period of incubation of the fungus, lesions resulting from this 
type of infection rarely become injurious on the fruit, except, perhaps, 
on late varieties. On the twigs and leaves, however, as was demon- 
strated in the inoculation experiments, secondary infections may be 
very abundant. Under orchard conditions such infections un- 
doubtedly account for a large percentage of the twig and leaf lesions 
which appear throughout the late summer and fall. 
OVERWINTERING OF THE FUNGUS. 
In considering the problem of how the fungus passes the winter, 
three major possibilities demand attention, viz, (1) the overwintering 
of conidia, (2) the overwintering of the mycelium in dead infected 
parts, and (3) the overwintering of the mycelium in lesions upon the 
living host. 
Careful studies of infected fruits, twigs, and leaves in late winter 
uniformly failed to reveal the presence of viable conidia. Further- 
more, the evidence furnished by the germination tests previously 
reported shows conclusively that when exposed under orchard con- 
ditions these conidia would not remain dormant and viable over 
winter. Even if they did pass the winter in minimal numbers, the 
conditions of infection, as set forth above, would make them a neg- 
ligible factor in the life history of the fungus. 
In the fall of 1913, portions of diseased fruits, twigs, and leaves from 
Cornelia, Ga., were exposed in the university orchard at Madison, 
Wis., and allowed to pass the winter. In the following spring conidia 
were produced in considerable numbers upon the fruit and twig frag- 
ments, and the fungus was readily isolated from each of these sources. 
The leaves, however, were badly decomposed, and the fungus was not 
identified upon them. 
At Cornelia, Ga., during the springs of 1912 and 1913, many over- 
wintered fruits and leaves from trees and from the ground were 
examined microscopically. The fungus was not definitely identified 
from any of these sources. It is quite probable, however, that under 
favorable circumstances the mycelium may survive the winter under 
orchard conditions upon fallen fruits, twigs, or leaves; but the 
evidence previously cited seems to prove conclusively that this type 
of overwintering is of no practical significance in the life history of 
the fungus. 
