FKUITS 237 



damage to American kinds. Dusting with sulphur is 

 a better remedy than the Bordeaux for this disease. 



Downy mildew (^Plasmopera) is a far more serious 

 trouble than the previous kind. This fungus grows 

 within the tissues of the leaves, sending out its fruit- 

 ing branches through the stomata on the under sur- 

 face, where they form a delicate downy or frostlike 

 coating. The affected leaves soon die and fall. 

 It also attacks and rots the young fruit clusters. 

 Fortunately, it can be controlled by thorough treat- 

 ment with Bordeaux mixture ; in fact, it was against 

 this disease that this famous remedy was first em- 

 ployed. 



Black rot (^Guignardia) should probably be con- 

 sidered the most "serious grape disease in eastern 

 North America. It grows on the leaves, causing a 

 conspicuous brown spotting, but its chief injury is 

 to the fruit. The infested fruits blacken and shrivel 

 into hard, unshapely, persistent masses, which are 

 covered with prominent pustules containing the 

 spores. This makes ragged, unsightly bunches that 

 are unfit for market. In severe attacks, all the fruits 

 on a cluster are frequently destroyed. Varieties 

 differ somewhat in susceptibility, but all of the bunch 

 grapes are more or less subject to attack, the rotiuidi- 

 folia type alone having any real immunity. Thorough 

 early and repeated spraying with Bordeaux, espe- 

 cially if continued from year to year, will usually 

 hold this disease in check, but it is notoriously diffi- 

 cult to control, and careless spraying is only wasted 

 labor. 



Ripe rot QCrlceospoymirn) is another very serious 



