170 MANUAL OF MODERN VITICULTURE. 



(C.) MILDEW.* 



This disease was first discovered in Europe in 1878 by 

 J. E. Planchon. Certain viticnltnrists thought they had seen 

 it before in many French vineyards, but it was most likely 

 confused with another disease, and they were not able to 

 assert that the disease they witnessed had the characteristics 

 of mildew. 



Since Planchon discovered it this disease has been found 

 in a great number of places in France, Italy, Spain, Greece, 

 Algeria, &c. It seems to have spread all over the Mediter- 

 ranean littoral. 



The consequences from a viticultural point of view are very 

 important. Mildewed vines do not ripen their fruit, give 

 weak wines, lacking in colour and keeping qualities ; the 

 wood is affected, and does not lignify. It is, therefore, with 

 .good reason that European viticulturists are greatly worried 

 at the progress this disease has made. 



ASPECT OF MILDEWED VINES. 



Leaves and shoots. On the under faces of the leaves wide 

 : spots appear, rather irregular in shape, and resembling a 

 saline efflorescence. Other spots correspond on the upper 

 faces. They have at first a yellowish tint, and gradually 

 .assume the colour of dead leaves. They are usually spread 

 over different points, generally limited by the veins, but 

 sometimes joining each other, and may cover the whole sur- 

 face of the leaves . 



The tissues of the parenchyma get destroyed in the places 

 where the spots appear ; if the disease lasts any length of 

 time holes soon replace the spots ; if the leaf is completely 

 attacked, it may be altogether destroyed and fall prematurely. 

 In some cases, as Prillieux ascertained, the limb becomes 

 detached from the upper part of the petiole. This is due to 

 the mortification of this organ and not to disarticulation. 



The white spots may sometimes be seen on the upper face 

 disseminated along the upper veins. Finally, when the 

 under face is much attacked by erijieum, the upper face often 

 becomes covered with white spots of mildew. 



Towards the end of the vegetating season the leaves get 

 -covered with yellow and brownish spots limited to the under 

 veins, which Cornu compares to tapestry stitches, and, later 



* Mildew or Downy Mildew h is not, up to the present, been identified here. [TranSls.] 



