10 Nov.. 1917.] Xotes on Downy Mildew. 685 



NOTES ON DOWNY MILDEW 



(Flasmopara viticola, B. and de T.) 



By F. de Castella, Government VUicuUurist, and C. C. Brittlebank, 

 Government Pathologist. 



Until last summer the vineyards of Australia were free from Downy 

 Mildew, tliat great scourge of vineyards in the nioister European climate. 

 It is true that one isolated case of the appearance of the fungus was 

 previously recorded, though it did not occur in a commercial vineyard. 

 The late Baron von Mueller, at that time Government Botanist, noticed 

 that a vine in hi.s private garden at South Yarra was afiFected by a 

 parasitic fungus, which he took to he ilildew; a diagnosis which was 

 confirmed by Dr. M. C. Oook, to whom specimens were sent. The Baron 

 eradicated and burnt the vine, and with this single exception the fungus 

 had not been observed on the Australian contin<>nt until last summer, 

 when it was found to be rather widely disseminated throughout the 

 north-eastern district of Victoria. 



Will the disease re-appear? Is it likely to give serious trouble? 

 What steps can best be taken to guard against such? These are ques- 

 tions which it is only logical to ask. The present season, being even 

 wetter than its predecessor, makes it extremely probable that we shall 

 again have the fungus with us. 



It is the object of the present article to briefly record last year's out- 

 break, to explain how tlie disease may be identified, and to point out 

 what preventive steps can best be taken to combat it, in the light of 

 recent European experience, should the disease again appear in our 

 vineyards. 



The 1917 Outbreak in North-East Victoria. 



On 31st January, 1917, whilst inspecting the Rutherglen Viticultural 

 Station, Mr. de Castella was informed by the vineyard manager that 

 a disease had appeared at the Wahgnnyah Xursery which differed from 

 ordinary Oidium. More detailed description aroused suspicions, which 

 were confirmed when the vineyard manager found a couple of similarly 

 affected leaves on a vine of Aramon Bouschet. These were immediately 

 posted to Melbourne, and were found by the Vegetable Pathologist (Mr. 

 C. C. Brittlebank) to be undoubtedly affected with Downy Mildew 

 Plasmopara viticola. The number of diseased leaves at the Viticul- 

 tural Station was exceedingly small. It was only after careful search 

 that any could be found showing the characteristic white down on the 

 under side. 



The Wahgunyah Nursery was inspected the following day; here the 

 fungus was very much more in evidence ; one block of Rutherglen Pedro 

 grafts was badly affected, nearly all the leaves being more or less con- 

 taminated, whilst some Muscat and Grenache showed the fungus to a 

 lesser extent. The greater part of the nursery, however, was practically 

 free from the fungus. Immediate spraying of the whole nursery with 

 copper soda was, nevertheless, ordered. 



At a vineyard a couple of miles up-stream from the nursery, and at 

 another 5 miles further up, leaves showing the characteristic white down 

 were also to be found, especially on vines close to the Murray River. A 



