10 Sept., 1918.] 



Downy Mildew. 



569 



affected, the damage was mainly due to Buncli Mildew or Grey Kot, 

 the most dreaded form of the disease. Within a few days of the first 

 manifestation, the bulk of the embryo bunches were white with the 

 efflorescence (Conidiophores) of the fungus; the crop was doomed. 



Appearance of the Disease in Other Parts of the State. 



The extension of the disease to other districts during the 1917-18 

 summer was characteristic of the extraordinary powers of dissemination 

 of the mildew fungus. Obviously, the date of first appearance could not 

 be accurately ascertained in every case, but the following notes as to 

 the dates on which the fungus was first identified in several districts 

 should prove of interest, as instancing its rapid spread; they should 



Ixg. 1. 



Grey Rot or Bunch Mildew . Diseased vines slioot 

 in e.irly spring — lower bunch covered witli 

 characteristic white down, which is also 

 visible on upper half of stem, the twisting of 

 which is due to fungus action. Reproduced 

 from Le Mildiou by L. Ravaz. (This form of 

 the disease was responsible for destruction lof 

 the grape crop in N.E. Victoria last spring). 



Fig. 2. 



Oil spots on upper side of leaf ; corresponding with 

 these on the undor-side, the white down 

 develops in moist weather. (After Ravaz)* 



serve as a warning to those districts which the fungus has not yet 

 reached. 



In the late autumn of 1917 the furthest point to which mildew had spread 

 appears to have been Glenrowan, some 40 miles as the crow flies from Ruther- 

 glen, where the disease was first found during the previous January. 

 It was subsequently identified at the following places: — 

 Violet Town, on the 11th December, 1917; 



In the Yarra Valley district, near Healesville, on the 18th January, 

 1918; within a few days the fungus was abundantly in evidence 

 throughout the whole Lilydale district. Healesville is distant from 

 Violet Town some 70 miles as the crow flies. In about a month the 

 fungus had thus traversed this distance and crossed the Dividing 

 Range. 

 At Sunbury, on 1st February ; 

 At Whittlesea, about the same date. 

 Meanwhile, the fungus had made its appearance at Tabilk, Shepparton, and 

 Mooroopna, in the Goulburn Valley. 



