52 MANUAL OF FRUIT DISEASES 
berry, oak, pine, rose, sumac, witch-hazel and others. In 
the spring the pycnospores emerge from the pycnidia beginning 
in April; this discharge goes on throughout the growing-season. 
The spores ooze from their pycnidia in coil-like masses ; the rain 
and wind carrying them to the leaves, fruits and bark. In- 
sects are not known to disseminate the fungus. Germination 
of the spores occurs within six hours, the tubes entering 
the various susceptible parts through wounds, except in the 
case of young leaves which are penetrated through the uninjured 
surface. Within a few days symptoms of the disease appear as 
already described. Pycnidia, in which spores develop, are soon 
formed on the affected organs of the apple. These spores are 
carried to other susceptible organs throughout the growing- 
season. Some of the spores may be disseminated to any of the 
many plants previously listed. With the advent of winter the 
fungus ceases its activities, and lives through the dormant 
season in the form of mycelium and spores in the cankers.¥ A 
perithecial stage is known, but it apparently plays no pr@mni- 
nent réle in the life-history of the pathogene. 
Control. 
The treatment of this disease consists in the eradication of 
cankers and in protecting the susceptible parts by the use of 
fungicides. 
The treatment of cankers may be followed along one of two 
lines. The affected limb may be cut from the tree, or the 
diseased bark may be removed. The grower must study the 
problem and must proceed in accordance with the conditions. 
The size and value of the limb and the extent of the infection 
will be criteria. Small limbs, that is, those with a diameter 
less than one inch, should in all cases be removed. It would 
rarely be profitable to attempt to treat a canker on a branch of 
this size. If the larger cankered limb is valuable because of its 
producing powers, then the size of the canker must finally de- 
termine the course to pursue. Smaller cankers on large pro- 
