GRAPE VINES DISEASES. 



3*5 



is the best preventive of aerial roots. If the border has become a close inert mass take 

 it away and supply fresh soil, for vines that have healthy roots and are not overdone 

 with moisture and warmth in the early stages of growth emit few or no aerial roots. 

 These, where the vines do not receive adequate supplies of nourishment through the 

 proper channels, are more beneficial than otherwise, and may remain to wither and die. 



GRAPE VINE DISEASES. 



There are only four fungous diseases of the grape vine in this country which occasion 

 sufficient damage to warrant attention : mildew, shanking, spot, and root-rot. 



Mildew. This is the name given to the whitish coating which covers the shoots, 

 leaves, and fruit, either in patches or extended 

 over large portions, and is caused by more than 

 one fungus. The most common and best-known 

 is Oidium Tackeri, so called after Mr. Tucker, 

 gardener to Mr. J. Slater, of Margate, in whose 

 vinery it was first noticed by the Kev. M. J. 

 Berkeley, in 1831, and described by him in 

 1847, when it was generally known. In 1848 

 it was noticed in France, in 1851 it had spread 

 to most vineyards in Europe, and in 1852 it was 

 found in Madeira. It had been known to exist 



manv vears previously in America, and, now that ,,. ... n . , 



J J J Fig. 103. OIDIUM TUCKERI (GEBATLY MAGNIFIED). 



it has been proved, as Mr. Berkeley suggested, 



to belong to Erisyphe communis a more fully developed form it may be considered 



a native of this country. 



The Oidium first appears as a mere speck, and spreads with amazing rapidity. The 

 diseased parts become pale and more or less distorted, then brown. When examined 

 with the microscope, the surface of the attacked part is shown to be covered with the 

 mycelium (filaments) of the fungus, and from the side of each little suckers push into the 

 skin (epiderm) cells, and these absorb food from them for the parasite. On the other 

 side of the mycelial threads spring little branches, each formed of a row of cells, of 

 which those at the ends of the branches (conidia) are oval, and break away to produce 

 the Oidium again when they fall on suitable vine-growths. The fungus as it appears 

 under the microscope is represented in the engraving, Fig. 103. The mildew proves 



