"DEAD ARM" OF GRAPE VINES.* 



F. H. HALL. 



The dead-arm disease of grapes is a widely 

 Disease often distributed trouble and in the aggregate does 

 overlooked, much harm in vineyards of the State. It, how- 

 ever, is not recognized as a disease by most 

 growers; and little or no effort is made to check its spread. The 

 attacks are very slow in developing to the final vine-killing stage 

 and affected plants are usually scattered promiscuously throughout 

 the vineyards, so the work of the disease is easily attributed to 

 accident, winter killing, general lack of vigor, etc., rather than to 

 the true cause, the fungus parasite, Cryptosporella viticola. 



Yet diseased vines have been found in practically every 

 vineyard examined, the percentage sometimes going as high as 5 

 per ct. in any particular season, with perhaps as many or more 

 new cases visible the following year. The trouble is found in 

 every grape-growing section of the State, though a cursory exami- 

 nation indicates that it may be less prevalent in the Keuka Lake 

 region than elsewhere. 



The most prominent indication of the presence 

 Symptoms. of the disease, at most times in the year, is the 

 dead arm which gives the trouble its name ; but an- 

 other striking symptom, visible only in June and early July, is the 

 peculiar yellow coloration of the foliage and the dwarfing, crimping 

 and curling of the leaves that mark affected portions of the vine. 

 (Plate VI.) The yellowing should attract the attention of every 

 grower during cultivation, and the diseased arm or vine should be 

 removed at once or marked for such treatment at pruning time. 

 There are several other less prominent signs of the disease, which 

 enable the expert to distinguish it from other troubles, but which 

 would not be so quickly noticed by the ordinary vineyardist. 

 These are peculiar, longitudinal, ribbed excrescences on the trunk 

 ■or arm, dry rot in the heart of the trunk and usually extending to 

 the margin, small reddish brown or black spots on the green shoots, 

 petioles, peduncles and leaf veins, and spotting and rotting of the 

 berries very similar to those produced by black rot. 



Reprint of Popular Edition of Bulletin No. 389; for Bulletin see p. 251. 



[953] 



