GRAPE PESTS AND THEIR CONTROL 225 



or "rattling." This premature dropping usually begins at 

 the end of a cluster, and clusters farthest from the trunk are 

 earliest affected. When vineyards suffer badly from this 

 shelling, the vines often take on a sickly appearance, the foliage 

 falling off in color and the outer margins of the leaves drying 

 up more or less. The fallen fruit has an insipid taste and is, 

 of course, worthless even if it could be harvested. 



The cause of the trouble is not known. Grapes may " rattle " 

 on high land or low land, on poor soil or rich soil, on heavy or 

 light soil. A vineyard may be affected one year and not the 

 next. Grape-growers usually attribute the trouble to faulty 

 nutrition, but applications of fertilizers have not proved a 

 preventive. Old and well-established vineyards seem freer 

 from the trouble than new and poorly established plantings. 

 The most reasonable theory as to the cause of shelling is that 

 it comes from faulty nutrition of the vine, but the conditions 

 so affecting the nutrition are not yet satisfactorily determined. 



Diseases of minor importance. 



Ripe-rot or bitter-rot (Glomerella rufomaculans) is a disease 

 due to the same fungus causing the bitter-rot of the apple. 

 As the name indicates, the disease usually appears on the fruit 

 at ripening time and under favorable conditions continues 

 after the grapes are picked. It may also attack the leaves and 

 stems. The first indication of the fungus is the appearance of 

 reddish-brown spots which spread and eventually cover the 

 whole fruit. The berries do not shrivel, but the rotted surface 

 becomes dotted with pustules in which the spores are borne. 

 It is hard to tell how much damage this disease does, but it 

 is not usually great and the late applications of bordeaux mix- 

 ture for black-rot or powdery-mildew are very effective in 

 controlling it. 



Crown-gall, now known to be a bacterial disease which causes 

 knots or galls on the roots of various wild and cultivated plants, 

 Q 



