224 MANUAL OF AMERICAN GRAPE-GROWING 



ing with bordeaux mixture, as recommended for black-rot, 

 is usually sufficient to keep the disease in check. 



Dead-arm disease. 



A troublesome disease of recent appearance is now doing 

 considerable damage in the Chautauqua grape-belt along the 

 shores of Lake Erie, being most common on the Concord. From 

 the fact that it is usually found on one arm of the vine it is 

 called "dead-arm disease 77 (Cryptosporella viticola.) The dis- 

 ease is caused by a fungus which passes the winter in small, 

 black fruiting bodies in the dead parts of the vine. Early 

 in the spring the fungus spreads by means of spores to the young 

 shoots and later in the season attacks mature berries, producing 

 small, black, oblong spots of black-rot. Sooner or later, if 

 the diseased shoot is not cut off, the fungus spreads to the arms 

 or trunk of the vine, producing a slow, dry rot which eventually 

 kills the affected part. Fortunately, the presence of the disease 

 is quickly detected by small yellowish leaves, much crimped 

 about the margin. 



The fungus is easily controlled by marking the diseased arms 

 when the first symptoms appear and cutting these off at prun- 

 ing time. If the vine is much mutilated by such pruning, 

 usually suckers can be brought up from beneath the surface 

 of the ground to renew the vine. The applications of bordeaux 

 mixture recommended for black-rot are valuable in preventing 

 the dead-arm disease. The disease is largely prevented by 

 renewing the old wood of the vine as soon as the trunk begins 

 to show a gnarled appearance. 



Shelling. 



In eastern America, especially in the Chautauqua grape- 

 belt, grape-growers not infrequently lose a large part of the 

 crop by the premature falling of the grapes from the stems. 

 The trouble is an ancient one and is designated as " shelling " 



