186 MANUAL OF MODERN VITICULTURE. 



a Black-rot has only exceptionally been detected on the 

 canes, petioles, and veins of the leaves. At first it has the 

 appearance of a large, black stain ; the fungus penetrates 

 inside the tissues and over the surface ; blisters, character- 

 izing the disease, may be seen. Finally, black-rot develops 

 but rarely on the parenchyma of young leaves. In this case 

 it is characterized by small stains, in two days both 

 faces of the leaf dry, leaving the fructifications of the 

 fungus apparent. The harm done on the leaves may be 

 overlooked."* 



The fungus is formed by the mycelium penetrating the 

 soft tissues, upon which it develops a series of conceptacles 

 <fpycnidia>) spermogonia,perithecia),vf\\ich contain the repro- 

 ductive bodies serving to propagate it. 



The disease appears to develop naturally in very damp 

 situations, and seems to more readily attack c6pages with 

 .juicy berries. The Ararnon amongst the vines of the South 

 was most attacked, and some years ago over half the crop 

 was lost through it (1885). 



Black-rot requires a high temperature and a great amount 

 of moisture to develop. This explains why it is only found 

 in the damp districts of the south and south-west of France. 



Means of combating the disease. The means used to 

 combat mildew have generally proved successful in prevent- 

 ing black-rot from developing, but to get good results 

 Bordeaux mixture of 3 per cent, strength should be used, 

 sprayed in such a way as to cover all parts of the plant up 

 to the extremities of the shoots. 



The first treatment should be applied as far as possible a 

 few days before the disease makes its appearance. This 

 means that we have to guess the right time, and sometimes 

 if the first appearance of the disease does not take place 

 as early as expected the treatment must be repeated. For 

 ultimate infections the maximum of action of copper salts 

 takes places two to five days after the acute period of 

 infection, that is to say, five to eight days after the 

 appearance of the first stains. It is therefore between 

 these two limits that the treatment should be applied, and 

 viticulturists should follow very closely the development of 

 the fungus in order not to miss the right time. 



The removal of stained leaves as soon as the disease is 

 -detected greatly retards the infection of the vineyard. This 



* P. Viala and L. Ravaz. Le Black-Rot Americain dans les VignoUes Fran?ais. Compt. 

 Rendus, 1886. 



