The Black-rot of the Grape, and its Control. 213 



infection from winter-spores took place June 30th and the 48 or 60 hours 

 of cloudy and rainy weather following. The spots appeared July 17th 

 and later. The vines were in full bloom June 28th and no doubt some 

 of the small berries were infected at this time, though the number was 

 comparatively small. The third infection took place from ascospores 

 also, for no pycnospores were mature at this time, and proved to be more 

 abundant on berries than any place else. The ascospore, if it has the 

 moisture, will penetrate the berry just as it did the leaf. The infection 

 came with the gentle rains of the nth and 12th of July, and the first 

 external indications appeared on July 21st and 22nd. 



Period of incubation. 



The period of incubation in the juicy berry is usually from 8 to 14 

 days at the end of which time a small circular, whitish spot i to 2 mm 



Fig. 1 82 — Showing stages in the rotting of the fruit. 



(1-12 in.) in diameter, appears. This enlarges rapidly and in 48 to 60 

 hours may involve half of the berry. About this time a blackening 

 appears at the center of the spot. This is caused by the formation on 

 the mycelium and just under the cuticle of the berry of a large number 

 of pycnidia. These form very rapidly and in 24 hours more than half 

 of the berry may have turned black. Thus it is that one ' frequently 

 hears it said, "the whole vineyard rotted down in a day," 



Black-rot on the berry. 



It occasionally happens that the effect on the berry is much like that 

 on the stem, so that a black crust is formed only on one side of the berry. 

 Usually, however, the whole berry is involved. By the time the whole 

 berry has become discolored, wrinkles are appearing on the side first 

 attacked and eventually the berry becomes wrinkled and black and dry. 

 (Fig'. 182). The pycnidia are very numerous on these mummified berries 



