10 Xov.. v.n; 



Xotcs on Downi/ Mildew. 



695 



Treatment. 



Tn view of tlie above, it is evident that the treatment used to comhat 

 Mildew must be radically different to that for Oidium, tlie exterior 

 myeclium of which is easily destroyed by dusting with sulphur, pro- 

 vided, of course, that weather conditions are suitable for its action. 

 The Mildew is, however, inside the tissues, where no spray can possibly 

 reach it. We can cure Oidium, but the treatment for Mildew must 

 be preventive. It is necessary to spray the vine with a substance 

 poisonous to the fungus, and in sufficient quantity for every rain or 

 dew drop to dissolve a sufficient proportion of the poison to prevent the 

 germination of any conidia which may fall into it. Various prepara- 

 tions of copper arc used for the purpose, the best known of which are 

 Bordeaux mixture and copper soda. They must be sufficiently insoluble 



Fig. 2. 



Downy Mildew — Plasmopara Viticola. 



Section of a vine leaf, late in the autumn, showing the wintering 

 form of the fungus, or oospores, buried in the tissue of the leaf. — 

 After Viala. 



to not be immediately washed off by rain and sufficiently soluble for 

 each rain or dew drop to be able to dissolve a trace of copper. These 

 preventive sprayings are capable of absolutely protecting the vine from 

 damage, though in very wet localities a large number of applications 

 may prove necessary. In districts of France where Mildew is not very- 

 severe, three sprayings are given; the first when the shoots are 6 to 8 

 inches long, the second after blossoming, and the third before the fruit 

 changes cqlour. These may be called the standard treatments, but in 

 very wet seasons additional ones are necessary. It is in this connexion 

 that knowledge of the period of incubation becomes of great value. It 

 Mildew spots are present in the oil-mark stage, they will not produce 

 conidia (no white down will be visible) until rain falls. Should this 



