18 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



THE GRAPE-SHRIVEL. 



The disease that we have denominated the Grape-shrivel is not as 

 yet, at least so far as known, of any great economic importance; but, 

 owing to the circumstances under which it occurs, it is highly probable 

 that it exists elsewhere in the reconstructed vineyards of California 

 and may, therefore, assume, at any moment, more than local interest. 

 The fact that we observed the Grape-shrivel in the East Sonoma 

 experiment plot, where it took the place of the Red-leaf disease, is sug- 

 gestive enough, even though it was not observed at either of the other 

 experiment plots, or in vineyards visited. 



Description of the Grape-Shrivel. The Grape-shrivel, as its name 

 implies, is characterized by the shriveling of the berries. In fact, this 

 shriveling is the only diagnostic character of this disease, the symptoms 

 which appear in the leaves being easily referable to drought, or imper- 

 fect nutrition. 



The Grape-shrivel develops quite rapidly, as shown by the fact that 

 while no symptoms of the disease were observed on the 27th of June, 

 yet on the 12th of July many vines were affected. By the end of July 

 practically every vine in the experiment plot showed the characteristic 

 shriveled grapes of this disease. 



The distribution of the Grape-shrivel is at first somewhat irregu- 

 lar, then general. The grapes on weak vines (not necessarily dying 

 vines) and strong vines are equally affected. The fruit on weak shoots 

 and strong shoots is affected alike. The general health of the vine 

 seems to bear no relation whatever to the distribution and intensity 

 of the disease. Vigorous, weakly arid dying vines (all with affected 

 grapes) commingle ; there are not the usual regular, or semi-regular, 

 depressed areas of vegetation so characteristic of parasitic diseases. 



Effect of the Disease on the Grapes. The Grape-shrivel, as already 

 mentioned, is characterized by its effect upon the fruit. The berries* 

 lose their clear, turgid appearance and become dull and flabby (but 

 never blotched, as in the Red-leaf disease), irregularly wrinkled and, 

 as it were, thick-skinned; as the drying progresses the wrinkling 

 becomes more pronounced and assumes a direction more nearly parallel 

 to the axis of the berry (Fig. 4). When completely dry the berries are 

 uniformly bluish, in some cases, where exposed to the sun, washed 

 with red; they are tightly shrunken around the seeds, and coriaceous. 

 At this stage the pedicels and the peduncle, to within a short distance 

 of the cane, are dried and discolored; the green and dried portions of 

 the peduncle become severed, and the completely desiccated bunch of 



*As we have only observed the Grape-shrivel on one variety of white grape (the 

 Sernillon) the description of the effect of the disease on the berries can only apply 

 integrally to varieties of the grapevine producing white fruit. 



