184 



MANUAL OF MODERN VITICULTURE. 



These mixtures have the same disadvantages as those 

 above studied. The first, however, should be preferred to 

 ordinary mixtures of sulphur and sulphate of copper, as far as 

 oidium is concerned, in countries where solar radiation is not 

 intense. The black colour due to the coal favours the 

 absorption of heat, and therefore the heating of the sulphur 

 and the disengagement of sulphurous acid, which acts as a 

 fungicide. 



These powders are applied with the machine used for 

 sulphuring (Fig. 152). They should be applied in the 

 morning when the leaves are covered with dew, to help their 

 adherence (Fig. 153). 



Nobody doubts the efficacy of copper salts against mildew, 

 but many people are alarmed at the idea that their appli- 

 cation might introduce into wine an element dangerous 



Fig. 152. Vermorel's Torpe.io Sulphuring 

 Machine. 



Fig. 153. Woman working a Torpedo 

 Sulphuring Machine. 



to public health. Experiments made in many places prove 

 that the copper is precipitated in an insoluble state in the 

 marc, and that the wines resulting from treated vines do not 

 contain measurable quantities of this metal. Sugar wines 

 and piquettes seem to realize the same conditions. Even 

 the consumption of table grapes treated with these mixtures 

 does not seem to have resulted in any accident. The treatment 

 of vines with copper salts must therefore be considered as 

 completely harmless to consumers. 



It results from the above studies that pulverized mixtures 

 do not give the same guarantee of success against mildew 



