16 



MANUAL OF FRUIT DISEASES 



graphical location, with the age and variety of the fruits con- 

 cerned, and with the weather. It is the rule that a fruit shows 

 but one or only a few spots (Fig. 5) ; but in cases of severe infec- 

 tion as many as 1200 separate lesions have been counted. Where 

 only a small number of spots occur these continue to enlarge, 



merging with each 

 other until the 

 whole fruit is in- 

 volved. If a great 

 number of lesions 

 begin simultane- 

 ously on the same 

 fruit, only a few 

 continue to spread, 

 the greater number 

 remaining as small, 

 brown, raised blis- 

 ters on the surface. 

 A lesion begins as 

 a small light-brown 

 discoloration be- 

 neath the skin. It 

 rapidly enlarges and 

 remains firm in tex- 

 ture and circular in 

 form (Fig. 5). The 

 color very soon be- 

 comes dark-brown and when about one-eighth of an inch in 

 diameter the rotted area is distinctly sunken and sharply defined. 

 When about one-half of an inch in diameter small black dots ap- 

 pear at more or less irregular intervals beneath the epidermis of 

 the sunken area. These may be arranged concentrically or 

 scattered without order (Fig. 5). Eventually these little black 

 dots, the fruiting pustules of the pathogene, break through the 



FIG. 5. Bitter-rot of apples. 



