PEACH DISEASES 295 
does not cause injury sufficient to make spraying for its control 
a profitable or necessary operation. 
Symptoms. 
The fruits, leaves and twigs are affected. On the fruit 
(Fig. 78) small, round, olive-black spots begin to show about 
six weeks after the blossoms fall, or from June 15 until July 10, 
depending on the variety. Lesions most frequently occur on 
the upper side of the fruit. If the spots are numerous, they 
coalesce, forming a large, irregular diseased area covering a 
greater portion of the fruit’s surface (Fig. 78) and preventing 
the normal expansion of the skin as well as interfering with 
Fic. 78. — Peach-scab; types of lesions on the fruit. 
the ripening and mellowing of the flesh. The fruit often be- 
comes one-sided, due to a formation of a protective cork-layer 
under the diseased area. This layer is incapable of further 
growth, and hence an ill-formed fruit results. Often the cork- 
layer is ruptured, leaving deep cracks (Fig. 78) through which 
the brown-rot pathogene enters (see page 275). Attacks are 
generally most noticeable on the late varieties, due, in part 
perhaps, to the fact that the fruit of such varieties is exposed to 
infection over a longer period. Of the commercial varieties, the 
Heath is said to be most susceptible. The Bilyen and Hill’s 
Chili are also badly affected, and the Salway, Smock and Morris’ 
White suffer severely. The Elberta is sometimes badly dis- 
eased, but is more resistant than those just mentioned. The 
Carman, Hiley, Champion and Belle are slightly affected. Trees 
