PLANT DISEASES 



441 



Stone fruit diseases. The common disease of stone fruits 

 is the " brown rot," and probably its destructiveness is 

 noticed more in the case of peaches than in any other one 

 of the stone fruits (plum and cherry), many of the " failures " 

 of the peach crop being due to it. Along with the peach 



FIG. 90. Potato disease ("potato rot ") in tubers. After DUGQAK. 



are associated its near relatives, the apricot and the nec- 

 tarine. In this case the fruit is infected directly by the 

 spores of the parasite, and it seems to be most susceptible 

 from the time it is half grown until it ripens. The first 

 symptom of the attack is a small, brown, decayed spot which 

 increases in size until the whole fruit is infected. Often the 



