TKEATMENT OF DISEASES INJURIOUS TO ORCHARD CROPS. 69 



that a mixture of copper sulphate and lime properly used on Grape foliage 

 prevents the attacks of Grape mildew. This preparation took the name of 

 Bordeaux Mixture. Since then many other preparations containing other 

 copper salts or various other poisons have from time to time been compared 

 with Bordeaux Mixture, but after much experimenting in this way the 

 Bordeaux Mixture has come out ahead of all competitors as a cheap and 

 effective preventive of certain plant diseases which are caused by attacks 

 of parasitic fungi. It has not been used with much success against 

 bacterial plant diseases. In 4;he treatment of certain superficial mildews, 

 such as the Gooseberry mildew, Sphcerotheca mors-uvcs, which is quite 

 destructive to English Gooseberries in America, potassium sulphide has 

 given better results. With these exceptions Bordeaux Mixture stands 

 to-day pre-eminently the best fungicide for use against those parasitic fungi 

 in general which attack the host plant through the leaves. 



Numerous scientific experiments, together with the lessons from 

 practical experience, have led to modifications from time to time of the 

 formulae and methods of preparing the material for spraying, and also of 

 the apparatus designed for applying the spray. 



Strength of Bordeaux Mixtiore. — When the Bordeaux Mixture first 

 came into use it was applied in the form of a comparatively thick heavy 

 mixture. Finally it was found that practically as good results were 

 obtained from the use of much thinner, weaker mixtures, which not only 

 had the advantage of being somewhat cheaper, but they were more easily 

 applied. In the Eastern United States it has been demonstrated that 

 formulae calling for one pound of copper sulphate to make ten or eleven 

 gallons of Bordeaux Mixture secure practically as good results in orchards 

 and vineyards as the old formula, which required one pound of copper 

 sulphate to make about four gallons of the mixture. In spraying Potato 

 plants to prevent mildew and mould, it has been found best to use some- 

 what stronger mixtures than those used in orchards, and in such treat- 

 ments, therefore, one pound of copper sulphate is used for making seven 

 or eight gallons of Bordeaux Mixture. 



Preparation of Bordeaux Mixture. — Several years ago Swingle called 

 attention to the advantage of diluting the ingredients of Bordeaux Mixture 

 as much as possible before mixing them.* This process insures a mixture 

 in which the solid particles remain in suspension for a remarkably long 

 time, and consequently the spraying apparatus by which it is applied is 

 less apt to become clogged than it is when the mixture is made 

 according to the old method of mixing the concentrated ingredients, and 

 afterwards diluting the mixture to the required strength. How much less 

 rapidly Bordeaux Mixture settles when prepared by the improved method, 

 than it does when made in the old way will be at once seen by comparing 

 figs. 9, 10, and 11, which are reproduced from actual photographs. And 

 this point is of especial importance where the spraying apparatus is run 

 by steam or horse power. It is then desirable to have a mixture of 

 uniform consistency at all times so as to avoid clogging the apparatus as 

 much as possible. 



When large quantities are to be used, it has been found convenient 

 for the preparation of the Bordeaux Mixture to keep constantly on hand 

 * Bui. 9, Div. Veg. Phys., U.S. Dept. Agr., 189G, 13. 



