REPORT OF TEE CHEMIST 149 



SESSIONAL PAPER No. 16 



CHEMISTEY OF INSECTICIDES AND EUNGICIDES. 



SODA-BORDEAUX OR BURGUNDY MIXTURE. 



During June and July of the present year a number of reports were received, botli 

 from Ontario and Quebec, stating that serious injury had resulted from the use of Soda 

 Bordeaux on apples, plums, cherries and peaches — in some instances the trees being en- 

 tirely defoliated. These communications were accompanied by requests for informa- 

 tion regarding this newly introduced mixture, in which washing soda is substituted 

 for lime, 



Soda-Bordeaux, which has been used successfully on potatoes for blight and rot, 

 may be prepared according to one or other of the following formulge: — 



A. B. 



Copper sulphate (Blue stone) 6 lbs. 4 lbs. 



Or^rbonate of soda (washing soda) 7i " 5 " 



Yv^ater 40 gals. ' 40 gals. 



The proportion of bluestone to washing soda is the same in each, but ' A ' is na- 

 turally the stronger spray. 



Though, as far as the writer can learn, Soda-Bordeaux mixture had not been sug- 

 gested for fruit trees, its use being mainly for potatoes, there appeared no reason 

 why it should prove injurious for orchard work. The explanation was furnished, when 

 upon further inquiry it was learnt that in every authenticated case in which injury 

 had been reported, Paris green, white arsenic or some other arsenical compound had been 

 added to the mixture. When Paris green is added to ordinary (lime) Bordeaux it is 

 not dissolved, but remains in suspension, and experience has shown that no injury to 

 foliage or fruit results from the use of such a spray. When, however, Paris green is 

 added to Burgundy mixture it is partly dissolved (owing to the excess of washing soda 

 present) and becomes an active arsenical compound more or less corrosive to foliage. 

 It has long been known that soluble arsenical compounds have this injurious effect and 

 that consequently they cannot be used in insecticidal mixtures. Paris green, arse^ile 

 of soda, and white arsenic were all reported as having been added to the Burgundy 

 mixture; all of these would render the spray extremely injurious. 



As it seemed desirable to furnish e:^erimental proof on this subject and since cer- 

 tain correspondents claimed that Burgundy mixture containing Paris green had been 

 used with impunity on fruit trees, a series of trials were made in the orchards of the 

 Experimental Earm, Ottawa, on apples, cherries and plums. In the absence of the 

 Horticulturist, these experiments were planned and carried through by myself. The 

 spraying mixtures were as follows : — 



' A ' — SODA-BORDEAUX. 



Copper sulphate (bluestone) 4 lbs. 



Carbonate of soda (washing soda) 5 lbs. 



Water 40 gals. 



The bluestone and washing soda were dissolved separately in half the total volume 

 of water and the resultant solutions mixed. This mixture, it will be observed, contains 

 no Paris green or arsenic in any form. 



'B.' — Soda-Bordeaux, as above, but to which 4 ounces of Paris green had been 

 added. 



* C — Soda-Bordeaux, as above, but to which a solution of arsenite of soda (formed 

 by boiling 8 ounces white arsenic and 2 lbs. washing soda with 1 gallon of water) had 

 been added. 



