424 - Bulletin 76, 



ium of the Uncinula so that the brown specks above mentioned, 

 [produced in the berries by the action of the suckers] if present at 

 all, are completely hid from view. These berries eventually be- 

 come dry and shrivelled, and finally drop off."* 



If the shelling of grapes as it occurred this fall were entirely due 

 to the presence of the powdery mildew, then the degree of shell- 

 ing should be directly in proportion to the severity of the attack 

 of the mildew. The vineyards, however, did not bear out this 

 proposition. Vines in which scarcely a trace of mildew could be 

 found, frequently lost a large amount of their fruit, and again 

 many clusters were seen having their stems literally covered with 

 the fungus, yet no berries fell to the ground. The frequency of 

 such cases has led me to believe that the powdery mildew is not 

 the principal cause of the shelling of grapes, although in certain 

 cases it may have exerted an influence in this direction, and pos- 

 sibly some berries fell from this cause alone. The cause for the 

 bulk of the shelling must be sought elsewhere. 



3. Blight of the foliage. — By the term " blight " is meant the 

 browning of the leaves as already fully described upon page 416. 

 Affected portions have been examined under the microscope but 

 no traces of insect or of fungous injury could be found. The 

 manner in which the leaf succumbs indicates that the trouble is 

 not local, but that something is wrong in the whole plant econ- 

 omy. Consequently it seems to be safe to say that the so-called 

 blight is not a cause of the shelling of grapes, but it rather ap- 

 pears to be a condition resulting from the same causes which make 

 the berries drop to the ground ; in other words, the browning and 

 dying of the edges of the leaves and of those portions situated 

 farthest from the main vines is to the leaf what the dropping of 

 the lower berries from a cluster is to that cluster. Neither is de- 

 pendent upon the other, and both are the result of some common 

 cause. 



*Scribner's Report on the Fungous Diseases of the Grape Vine. U. S 

 Dept. of Agric. Bot. Div. Sec. of Veg. Path. Bull. II. p. 22. 



