PEAR DISEASES 335 
ment. However, much of the food for the fungus no doubt 
comes from the attacked cuticle. 
Infection of the various parts continues throughout the grow- 
ing season. In the fall the affected leaves drop to the ground, 
carrying the fungus with them. Soon the mycelium changes its 
superficial habit and permeates the entire leaf. Before cold 
weather, perithecia begin their development within the old 
dead leaf-tissues. These bodies remain immature until spring, 
when they resume growth. This begins at least by the time 
the pear-tree starts into growth. By the time the blossom- 
buds are showing white the perithecia contain mature asco- 
spores which are discharged during periods of moisture. Their 
ejection is accomplished with force enough to carry them into 
the air, where they are easily caught by the wind and are blown 
to the opening buds. The germination of these spores finally 
results in infection. The period over which ascospores are dis- 
charged is not definitely known, but reasoning from the known 
facts concerning the apple-scab fungus the period probably 
extends over several days. 
The pear-scab fungus also passes the winter on the twigs. 
The mycelium and conidia remain alive from autumn until 
spring, when new infections are initiated. Twigs are commonly 
affected, so that this method of hibernation is unquestionably of 
considerable importance. It is not known nor believed to be 
true that the fungus winters over on fallen fruit. 
Control. 
Pear-scab, although found everywhere, can be controlled 
effectively. That it is not held in check in many orchards where 
spraying for it is done is no indication that it cannot be 
prevented. Time and thoroughness of the applications of 
fungicides are of prime importance. 
The number of sprayings will depend somewhat on the-his- 
tory of the management of the orchard in the past. If. the 
orchard has been well sprayed, three applications will suffice 
