14 



BLACK ROT OF THE GRAPE, (Laestadia BidioelUL) 



This fungus attacks the fiuit and sometimes the leaves. It first 

 appears as a light brown spot, spreading rapidly if the weather is 

 warm and moist, and quickly covering the entire berry, which then 

 presents a gray, brown color. When attacked earlj' in the season, 

 the berry shrivels and turns a dark blue or black color, but if it 

 comes when the berries are nearly full grown, they soon rattle from 

 the bunch when handled. It is found more or less throughout the 

 country, but only locally in New England, and has not done serious 

 injury until within a few years. It seems to be increasing in Massa- 

 chusetts, 



THE POTATO-ROT FUNGUS, 

 (Phytophthora [^Peronospora^ infestans.) 



While closely related to the grape mildew it is placed by some 

 authorities in another genus. It attacks both the foliage and the 

 tuber, causing what is called the blight of the vines, in the one, and 

 the rot of the tuber in the other. To the casual observer, its first 

 appearance on the leaf is in the yellow spots and powdery or mealy 

 substance dn the surface, which is the fruiting stage of the plant 

 that lias been feeding in the substance of the leaf tissue. These 

 spots soon turn brown and the whole plant becomes infested and 

 dies. In moist, warm weather the growth of this fungus is so rapid 

 that it requires but a few days to destroy acres of potato tops. 



It the leaf spores come in contact with the tubers, or if the rooting 

 or feeding parts of the fungus press through the stems to them, they 

 rot, provided the warm, moist weather continues. In seasons when 

 the atmospliere is cool, the tops are not attacked, and if the soil 

 remains cool the tubers will often escape when the tops are destroyed. 



BLACK WART OF THE PLUM AND CHERRY. 



(Ploivrightia \^Sphoeria^ morhosa.) 

 The black excrescences called black knots or warts on the plum 



and some kinds of cherry trees, are the result of a fungous growth, 



the spores of which have germinated during moist weather of the 



early summer, and penetrated the tissues. 



The excrescence is the growth of the fungus and the effort of the 



tree to overcome the injury. Spores are scattered from the surface 



