New York Agricultural Experiment Station. 255 



(e) A dry rot in the heart of the trunk and usually extending 

 to the margin is more or less characteristic. (Fig. 7.) 



(f) The small 

 reddish brown or 

 black spots on 

 the green shoots,] 

 petioles, ped- 

 uncles, and leaf 

 veins are very 

 characteristic. 

 Sometimes they 

 flr p deen and the ^ IG ' ^' — Cross Sections of Diseased Niagara Trunks 



" Showing Characteristic Necrotic Effect. 



shoot shows 



narrow V-shaped slits; at other times the spots are more superficial 



but are so numerous as to make a continuous diseased area for 



some distance on the shoot. In very severe cases the lesions are 



deeper and the V-shaped slits mentioned above extend for some 



distance, usually from one to three inches, up and down the shoot. 



Fig. 5 (Plate VII). These lesions are discernible the following 



spring as reddish elevations, or as a noticeable longitudinal cracking 



or stringing of the fibres. 



(g) The occurrence of the disease on ripe or nearly ripened berries 

 has been found repeatedly on Niagara grapes at Romulus, N. Y., 

 by Mr. C. T. Gregory (1913). The disease is scarcely distinguishable 

 from black rot except on very careful examination. Usually it is 

 necessary to use the microscope to confirm a diagnosis with any 

 degree of certainty. The berry shrivels (Fig. 6 — Plate VII) to a 

 mummy as in the case of black rot but has a slightly more grayish 

 appearance and the pustules which occur so thickly over the surface 

 of a black-rot berry are more scattered in the case of this rot. 



etiology. 



The cause of this disease is a fungous parasite technically known 

 as Cryptosporella viticola Shear. The fungus was apparently first 



Isolations made from an old arm near the first wire of the vine shown in figure 

 45 and from various places in and above the lesion shown in figure 47 gave 

 numerous pure cultures of the causal organism of dead arm. The vine in figure 

 45 has been visited every year since the photograph was taken. In July, 1910, 

 some of the shoots showed evident lesions of the dead-arm fungus. In 1912 the 

 vine bore a good crop of fruit although the lesions of crown gall were about as 

 abundant as in the photograph. 



