EXPERIMENT STATION BULLETINS. 353 



Like the black rot the bitter rot is most i)roniinpnt on the fruit. Infected 

 apples show brown spots which rapidly enlarge until the whole fruit is involved. 

 Small pimples soon ai)pear in concentric order around the points of infection. 

 From these pustules the spores ooze out, showing; a pinkish color in mass, and 

 are washed on to other apples by rain, or becoming dry, may be carried away 

 on currents of air. A rcsting-spore stage is also known to occur on apples which 

 have rotted with this disease, and this is one means by which it is carried through 

 the winter. An investigation of the disease of bitter rot conducted by Von 

 Schrank and Spalding in 1901 and 1902 revealed the fact that the chief source 

 of infection arises from a permanent or winter stage of the disease in the form 

 of cankers on the limbs of the apple tree. 



Apples affected with this disease commonly possess a bitter taste although this 

 is not always the case. 



Bitter rot is very destructive in some of the more southern states, being especi- 

 ally bad in Southern Illinois, where it is the chief apple rot. Its presence in 

 Michigan has been noticed as somewhat uncommon. The writer has found it on 

 Pennock's red stored in a cellar and on packed Greenings. Ben Davis and 

 Grimes' Golden are recorded as varieties most subject to this disease in Illinois. 

 This fungus also occurs on the grape, pear, peach, quince and even on tomatoes. 



The preventive measures and other treatment for this disease are practically 

 the same as for the black rot fungus. Destruction of old diseased fruit and the 

 removal of cankered limbs wherever found are to be practiced. Spraying to be 

 successful should be begun before the disease appears. 



BLACK KOT. 



(Sphaeropsis malorum Berk.) 



Fig. 6. —An apple affected with the black rot fungus, showing the wrinkled condition and dark color 

 of the dry fruit which is often found hanging on the trees, or lying on the ground over winter. 



Black rot is a common disease, especially on fruit of summer and fall varieties 

 of apples. These are attacked usually when nearly mature and ofen while still 

 hanging on the tree. Apples affected with this disease decay I'apidly, becoming 

 brown at first, with blackish discolorations under the skin. As the disease pro- 

 gresses the black color spreads until the fruit may become entirely blackened. 

 The apples retain their firmness for some time, and then gradually dry out, be- 



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