434 



"White Rot" of Vines. 



[OCT., 



This disease is due to the presence of a minute parasitic 



fungus called Coniothyrmm diplodiella. On the Continent 



it attacks vines growing in the open air, 



"White Rot" a nd during recent years has frequently 

 of Vines. , . , . . / 



been met with on vines growing under 



glass in this country. 



The fruit is the part most frequently attacked, and in severe 

 cases the fungus spreads from the stalk of the bunch of fruit to 

 the branch from which it springs ; the foliage is unaffected. 

 When once established, the disease spreads rapidly, and usually 

 every grape on a bunch becomes diseased, owing to the numerous 

 minute spores of the fungus being conveyed by rain, syringing, 

 &c, from diseased to healthy berries. During the first stage of 

 disease the berries become pale brown in colour, and soon 

 commence to shrivel, but do not fall. At a later stage, when 

 the shrivelled berries have become dry, the skin is covered with 

 minute whitish pimples representing the fruit of the fungus. 



When the stalk of a diseased bunch is attacked, the fungus 

 often passes on to the branch, where it forms slightly depressed 

 areas, which are at first brownish in colour, but afterwards 

 studded with the characteristic white pustules of fungus fruit. 

 The diseased patches may extend for several inches down one 

 side, or the branch may be completely girdled by a zone of 

 diseased tissue, and if this is the case that portion of the branch 

 above the injured zone soon dies. In vineyards the disease is 

 most injurious during seasons of great humidity accompanied 

 by warmth. Under such conditions one-quarter to one-third of 

 the crop may be destroyed within the space of a few hours. 



The best remedy is to remove and burn all diseased bunches 

 of fruit, and spray every part thoroughly once every five days 

 with a rose-red solution of permanganate of potash. 



If the disease is of recent origin and confined to the bunches 

 of fruit, the above treatment will suffice. If, however, the disease 

 has spread to the branches, its presence will be indicated by 

 the slightly depressed whitish patches on the bark already 

 mentioned. All such diseased branches should be cut out,. as 

 spraying will not check the disease on permanent parts of the 

 vine. 



