234 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



rest by the verdure of the leaves, and by the perfect health of the- 

 grapes. Owing to experiments made by Millardet and Jouet, it was. 

 found that this fortunate action was to be attributed to the copper and 

 not to its lime. This empirical remedy was thus recommended to com- 

 bat mildew, under the name of bouillie bordelaise. In the beginning- 

 the bouillie bordelaise was much stronger than now. It consisted of 

 15 per cent of lime and 8 per cent of blue vitriol. This bouillie was 

 spread on the vine by means of small heather brooms, for its consist- 

 ency did not allow the use of a spraying machine. From year to 

 year the dose of blue vitriol was diminished, and the lime, an excess- 

 of which was found useless, was reduced to the dose strictly necessary. 

 In 1887 bouillie bordelaise consisted of 'S per cent of blue vitriol and 1 

 per cent of quicklime. Millardet and Gayon had already experimented 

 at this time with weaker bouillies, with 2 per cent, and even 1 per 

 cent of blue vitriol. As these bouillies produced the same effect, they 

 regarded them as efficient and recommended several sprayings with a 

 1 per cent bouillie in preference to a single spraying with a 3 per cent 

 bouillie of blue vitriol. These results were published in 1888, and 

 spread the formula of the new bouillie over the whole world, where it 

 was adopted as the normal bouillie. Owing to a great increase in the 

 price of blue vitriol it was tried to reduce the amount of blue vitriol 

 entering into the bouillie. Guocdenovic has shown that a 0"5 per 

 cent bouillie suffices in all cases. Zweifler extended his experiments' 

 from 2 per cent to 0-1 per cent bouillie, and concluded that 0*5 per 

 cent of blue vitriol was sufficient — an efficient bouillie against mildew. 

 These proportions are used on the large scale and with great success- 

 in Italy and the Tyrol. Used at first exclusively against mildew it 

 has been found that bouillie bordelaise is perfectly capable of combat- 

 ing a great number of other diseases. 



Practical Spraying. — The less cupric hydrate in the bouillie the 

 greater must be the number of sprayings. Eepeated spraying against 

 plant diseases is in general favourable, because only the organs of the 

 plant reached are rendered invulnerable, so far as wind and rain have 

 not removed the preservative layer of copper oxide. To preserve a 

 plant for the whole year from disease, the growth of the spores of 

 parasitic fungi must be stopped. As there is a continual growth of 

 new leaves uncovered by bouillie bordelaise, several sprayings must be- 

 applied preferably during fructification of the fungi, and especially 

 during the germination of their spores. To prevent plant disease by 

 bouillie bordelaise it is necessary — 



1. That the bouillie be made conscientiously according to the pre- 

 ceeding rules. Bouillie bordelaise is mostly used neutral. However, 

 numerous experiments by Mader, Bain, Sturgis, and Aderhold have 

 shown that in certain special cases it is better to use bouillies containing 

 an excess of lime. Certain fruit trees, sensitive to neutral bouillie 

 bordelaise as much as to pure blue vitriol, are so no longer when there 

 is excess of lime. Against the cryptogamic diseases of the apple and; 

 peach trees, it is well to use O'o per cent of blue vitriol and 4 per cent 

 of quicklime. 



2. That the evolution of the disease to be fought against be- 



