574 Journal of Agriculture, Victoria. 1 10 Sept., 1918. 



season. In reality, it is not one unique invasion which has to be com- 

 bated, but a series of them, one (or more) of which may be of far greater 

 intensity than its predecessor. In the French climate, there are often 

 several intense invasions in a season, hence repeated spraying is neces- 

 sary. Here, where it is hoped that one spring spraying may suffice, it 

 will be essential to provide against the first dangerous infection, and to 

 .thoroughly spray the vines immediately before it takes place. 



As a rule, the first invasion — that resulting from oospore germina- 

 tion — is on a limited scale, though it is possible to imagine weather con- 

 ditions such as would permit of its being widespread. Even if slight, 

 it will, after seven days' incubation, result in the appearance of a greater 

 or lesser number of oil-spots, which will (weather, of course, permitting) 

 provide abundant spores for further and more general invasion. 



In France, until recently, dates for spraying were more or less arbi- 

 trarily fixed. Most of the older text books recommend a first spraying 

 three weeks before blossom, a second at blossoming time, a third a month 

 later, and a fourth a month later still. This course has recently been ad- 

 versely criticised. In the cold French spring, mildew often fails to appear 

 in May (November here), in which case the first spraying would be 

 wasted. Fixing the dates according to the development of the fungus is 

 far more logical. 



In Victoria, we have only one year's experience of the fungus; un- 

 fortunately, a disastrous one. At Mount Ophir, where 95 per cent, of 

 the crop was saved on the portion of the vineyard which was sprayed, 

 this work was commenced on the 24th October, and continued with good 

 results until early in November (about the 5th). Any spraying carried 

 out later proved quite powerless to save the crop. Should this coming 

 spring prove similar to the last, it would be safe to await the 20ith 

 October before spraying. We may, however, have an earlier spring than 

 last year, in which case oospore germination (the first invasion) might 

 be advanced somewhat. Earlier spraying than last year would then be 

 desirable. 



Owing to similarity of climate, Algerian experience of mildew should 

 prove of considerable value to us. In that country, the date of first 

 appearance varies greatly from season to season. During the past ten 

 years it has seldom been reported before the. latter part of May (No- 

 vember here), whilst in some years it has not shown up before June or 

 even July. Its first appearance in May (or earlier) was in the years 

 1908, 1909, 1913, 1915, 1916 and 1918. In only two of these was it 

 observed before the middle of the month, viz., in 1918, quite earlv 

 May, and 1916, when it was first observed at the end of March (Sep- 

 tember here) and beginning of April (October here), though early 

 spraying and timely hot winds (Siroco) prevented serious damage. A 

 similarly early start is by no means impossible in our climate which, 

 at least on the Murray, is warmer than most of Algeria. An earlier 

 outbreak than that of last year may, therefore, have to be reckoned 

 with in some seasons. 



In a general way, and as far as it is humanly possible to predict, it 

 may be laid down that spraying should be completed by the 20th Octo- 

 ber"! Needless to say, the closest possible watch should be kept for the 

 very first manifestations of the disease; but whether it show up or not. 

 spraying should be proceeded with, and completed by the above date. 



