September 21. 1907 



HORTICULTURE 



4ai 



BORDEAUX MIXTURE. 



It may seem that the subject of Bor- 

 deaux Mixture has been pretty thor- 

 oughly considered, but so many ques- 

 tions are constantly sent to experi- 

 ment stations and publications in re- 

 gard to its manufacture and use that 

 a discussion may not be out of place. 

 Its Discovery. , 



In all bulletins and articles pub- 

 lished on plant diseases, Bordeaux 

 Mixture plays a very important part 

 In the recommendations for treatment. 

 It was accidentally discovered m 

 France in the little town 

 of Bordeaux, about 1SS2, by 

 a man named Millardet. He was 

 losing many of his grapes near 

 the road from depredations of passers- 

 by, so to protect them he covered the 

 vines with a coating made of copper 

 sulphate and lime. In the fall there 

 was such a noticeable difference, in 

 amount of mildew, between those 

 treated rows and the rest of the field 

 that he observed it. By further ex- 

 perimenting, the value of Bordeaux 

 Mixture was discovered. 



Its Composition. 



As ordinarily prepared, Bordeaux 

 Mixture is a thick, sluggish, bluish 

 liquid composed of copper sulphate 

 and lime carried in water. The fungi- 

 cidal value comes from the copper, 

 Cine-millionth part being often suffi- 

 cient to destroy plant life. It the cop- 

 per sulphate (commonly called 'blue- 

 stone") is dissolved in water it will 

 have the same effect as the mixture. 

 but it has the disadvantage of being 

 quickly washed off the trees, and fur- 

 thermore, has a tendency to burn tho 

 foliage, especially where large drops 

 collect. The lime in the Bordeaux 

 Mixture, on the other hand, forms 

 compounds which act as carriers and 

 retainers, liberating but a little of the 

 copper at a time. As a very small 

 Quantity is all that is needed, a good 



ll.iking Bor.lriiH\ Mixinir ;iiid a llain 



coating will last through several very 

 heavy, prolonged rains. And the lime 

 prevents burning, thus doing away 

 with the second objection. 



An amateur perusing technical bul- 

 letins dealing with this subject is very 

 likely to become confused over the 

 large number of formulas, different 

 ones often being mentioned lor the 

 same purpose. The .5-5-.50 may be con- 

 sidered the basis of them all. This 

 means five iiounds of bluestone and 

 five pounds of lime to fifty 

 gallons of water. For different 

 plants and different diseases this 

 is changed to some extent. For 

 instance, dormant trees can stand a 

 heavier dose than those in full leaf. 

 The peach is more liable to suffer from 

 an ordinary formula than the apple or 

 pear, and this susceptiblity has to be 

 taken into accoiint. Some men over- 

 come this by adding an excess of lime, 

 others by using less basic material. 

 And so it goes. A carefully made for- 

 mula may safely vary 'a little provided 

 there is an equal or excess amount ol" 

 lime. A wealc one carefully made and 

 well applied will give better results 

 than a strong formula hastily put to- 

 gether and carelesssly squirted on. 



i'jiie Willi a 



It seems a very easy matter to put 

 copper sulphate and lime together in 

 water, but the actions which take 

 place are very complex, and in fact, 

 not well understood by the chemists. 

 In general, the lime which is calcium 

 hydroxide, has a stronger affinity for 

 copper than the sulphiu'ic acid, and 

 when the twr' ingredients are put to- 

 gether calcium copper hydroxide comes 

 down as a soft, light blue precipitate 

 while some of the lime is given up and 

 unites with the acid to form calcium 

 sulphate. But there are a number of 

 minor changes, especially with impure 

 materials. A knowledge of these is 

 not important, only in so much as they 

 show the need of very thorough meth- 

 ods to insure a proper mixture. 

 Its Preparation. 



The preparation of the 5-5-50 formu- 

 la will serve as an illustration. Let 

 lis suppose we are to make a hundred 

 gallons of prepared spray. Good lumps 

 of unslaked lime are secured, the best 

 coming from the centre of the barrel. 

 Ten pounds is carefully weighed out 

 (twice the amount called for in the 

 formula, for the hundred gallons) , and 

 placed in a bucket or half barrel, ft 

 is then carefully slaked by adding 

 water, using only enough to keep the 

 mass dampened and repeating fre- 

 quently to prevent burning. When 

 thoroughly slaked the lime should be 

 pasty, a little rubbed between the 

 thumb and finger giving no sensation ' 

 of grit or coarseness. When this is 

 obtained, a very good Bordeaux can be 

 made. Meanwhile the ten pounds of 

 bluestone should be dissolving. It can 

 be put in the night before if so desired. 

 A quick way is to put the bluestone in 

 a burlap L^ag and suspend this in a bav- 

 rel or tub. No metal receptacles will 

 do, for the copper corrodes most of 

 the common kinds. Hot water will 

 also hasten dissolving. 



.Just previous to using the Bordeaux 

 mixture, one-half the lime is placed in 

 a barrel and diluted with clean water 

 to twenty-five gallons. One half the 

 bluestone water is also brought up to 

 twenty-five gallons in another barrel. 

 Then by pouring the lime water and 

 bluestone solution simultaneously pail 

 liy pail through a sieve into a third 

 barrel a complete Bordeaux Mixture 

 will result, which will stay in suspen- 

 sion and give the best results when 



