858 THE FRUIT INDUSTRY IN NEW YORK STATE 



are usually numerous about the blossom end of the fruit. The 

 spots show a whitish, papery margin and a velvety brown center. 

 As they grow older the velvety center disappears, exposing a 

 brown corky layer beneath. This frequently cracks and checks. 

 Later infections that is, those appearing about picking time or 

 after the fruit is stored are very different in appearance from 

 the early infections; they are much smaller, being mere black 

 specks. 



In the autumn the leaves fall to the ground, taking the fungus 

 with them. There it changes from its superficial habit to one 

 involving the whole leaf. The winter fruiting bodies (the 

 perithecia) are soon developed, in which condition the fungus 

 again lives until spring. 



Influence of the \Veather on the Disease 



It is clearly understood, then, that the scab is a fungous 

 disease, and is not caused by weather conditions. To be sure, the 

 weather is the most important environmental factor iiimienc- 

 ing the disease, but unless the fungus is present there will be no 

 scab. The weather influences the disease by affecting both the 

 fungus and the apple tree. If rain falls just before the blossoms 

 open, the mature ascospores are discharged and infection results 

 on young leaves and pedicels. If the ascospores are not dis- 

 charged by the rains until just after the blossoms open, infection 

 of the developing fruits occurs. 



If these first infections do not occur within a month after the 

 blossoms begin to open, it is likely that infections will be few 

 and unimportant during the season. 



Controlling the Disease 



In controlling scab the following points should be taken into 

 consideration: (1) the fungus winters over in the old leaves on 

 the ground; (2) the spores therefrom are discharged at about 

 blossoming time during a period of a month, rain being necessary 

 to this discharge; (3) the opening leaves and fruit stalks are first 

 liable to infection, and later other leaves and growing fruits are 

 subject to it. Plowing under the old leaves which harbor the 

 fungus would seem advisable. This has been frequently recom- 



