DEAD-ARM DISEASE OF GRAPES.* 



DONALD REDDICK.t 



SUMMARY. 



The dead-arm disease of grapes occurs in the majority of vine- 

 yards of the State, where it takes an annual toll from the income 

 of the vineyardist. The most striking symptoms of the disease 

 are the presence of bare arms in the spring and the occurrence of 

 dwarfed, crinkled, yellowish-colored leaves during the early part 

 of the growing season. 



The cause of the disease has been determined to be the fungus, 

 Cryptosporella viticola. The fungus has been studied and its 

 pathogenicity established by numerous inoculation experiments. 

 Infection of new shoots occurs from spores produced in the fruiting 

 bodies of the fungus which develop on tissue killed the previous year. 

 Preserving infected canes for bearing wood is thought to be the 

 chief means by which the fungus gains entrance into the arms and 

 trunk. The fungus rarely passes down the trunk to subterranean 

 parts. 



The chief method of control lies in marking and removing all 

 vines showing symptoms of the disease. Suckers originating from 

 beneath the surface of the ground almost invariably develop strong 

 and vigorous vines unless infected by spores during the first few 

 weeks of their development. Those originating above the surface 

 of the ground develop healthy plants unless the fungus has grown 

 down the old trunk to the point of issuance of the shoot in which 

 case the renewal usually dies in its second or third year. 



INTRODUCTION. 



In a bulletin of the Cornell University Agricultural Experiment 

 Station (No. 263, February, 1909), the writer l published a pre- 



* Reprint of Bulletin No. 389, July; for Popular Edition see p. 953. 



t Formerly Assistant Botanist of this Station, connected with Chautauqua 

 Grape Culture Investigations; now Professor of Plant Pathology, Cornell 

 University. 



1 For this and similar references to literature, see Bibliography, p. 277. 



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