224 THE APPLE 



Bitter rot is caused by a fungus, and not by wet weather as many 

 growers believe. Hot, muggy, or showery weather in summer is 

 the most important factor in the development and spread of the 

 disease. Where such weather conditions obtain for any length of 

 time after apples are half grown, bitter rot is almost certain to de- 

 velop. Rains spread the disease by washing the spores from affected 

 fruits to healthy fruits. The rot usually does not appear on the 

 fruit until the early part of July. It makes its first appearance on 



% h-A . 



Fig. ioo. Bitter rot. (University of Maine) 



the apple as very small, brownish-colored specks beneath the skin, 

 which grow quickly, assuming a circular outline. The diseased area 

 becomes sunken and increases rapidly, the infection radiating by 

 concentric rings with clear-cut margins. The mycelium of the fun- 

 gus penetrates the flesh of the fruit, involving the tissues in a soft, 

 brownish, cone-shaped decomposition. The small black spots which 

 appear beneath the skin of the diseased circles finally break through 

 and give off the spores or seeds of the disease. The spore masses 

 are pinkish in color, and are readily washed about by rain and 



