248 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



Exoascus Priini (pockets of the plum). — Sturgis asserts that he 

 obtained a radical cure of the disease by bouillie bordelaise. 



Er)j.'ii])]tc commiuiis, Wallr. (mildew of the pea). — This mildew- 

 is successfully treated by sulphur. Nijpels asserts that one or more 

 sprayings with bouillie bordelaise likewise cures the disease. 



Uncinula arnericana. How. (oidium of the vine). — The mycelium 

 crawls on the surface of the leaf and there produces its organs of re- 

 production. It was possible that this fungus, protected less than any 

 other by the tissues of the nurse plant, might be readily destroyed by 

 copper salts. It was also hoped to be able to suppress the sulphurat- 

 ing used against this disease by replacing it by vitriolization. This 

 process would have much simplified the dressings required against the 

 cryptogamic diseases. Neither blue vitriol nor cupric hydrate have, 

 however, any curative or preventive action on this fungus, and it 

 vegetates quite as well on leaves covered with bouillie bordelaise as 

 on untreated leaves. The treatment for mildew being an absolute 

 failure against oidium, it remains necessary to continue the sulphurating 

 of the vines at the same time as the vitriolizing with bouillie bordelaise. 

 Up to 1902 it was thought preferable to separate the two treatments. 

 It seemed in the beginning that there was no drawback in the 

 fact that one of the operations was conducted before the other, and it 

 was the sulphuring, as the oldest known, with which the vine-growers 

 began ; but in considering the mechanical phenomena which ai-e pro- 

 duced in this case on the surface of the leaf, it will be understood 

 why it is necessary to precede the first sulphuring by vitriolizing. If 

 the first treatment be sulphuring, the sulphur deposited on the leaves 

 mechanically fixes a large part of the bouillie, which will not adhere 

 to the leaves, and forms large uncovered spaces. There is really 

 neither complete sulphuring nor vitriolizing. If, on the other hand, 

 we vitriolize first and sulphur as soon as the spray is dry, the adher- 

 ence of the sulphur is increased, and the two remedies have their full 

 action on the cryptogamic diseases which they should overcome. To 

 simplify the work of the vine-grower it has been tried to unite these 

 two treatments in a single one ; say by mixing the sulphur with finely 

 pulverized copper salt, or by mixing the sulphur in the cupric bouillie. 

 In the beginning the use of these mixtures often gave negative or very 

 incomplete results, so that Polacci, P. Viala, Mach, and Mart's have 

 condemned them as unfit to cure or preserve the vine from 

 oidium or mildew, because the copper salts by seizing the vapours of 

 sulphur poisonous to the oidium converted them into copper sulphide, 

 inert towards mildew. In 1902 Guillon reported to the Academy of 

 Sciences the altogether satisfactory results obtained with sulphurated 

 bouillie bordelaise in the Charente. Without denying the reactions 

 which may occur between copper derivatives and sulphur, Guillon has, 

 however, observed that these are slow to occur, and that bouillies 

 sulphurated immediately after their preparation may act simultaneously 

 oil the two diseases before the sulphur has acted on the cupric hydrate. 

 To mix the sulphur in the bouillie it is necessary to moisten it suitably. 

 For this purpose water or the bouillie must be allowed to fall, drop 

 by drop, on the sulphur whilst stirring. It is, however, preferable to 



