PROCEEDINGS, 1918 51 



A MODIFIED BORDEAUX MIXTURE FOR USE IN 

 APPLE SPRAYING. 



by 



G. E. Sanders, W. H. Brittain, 



Field Officer in Charge ^ ••1^4- 1 • +. 



~ „ , 1 • 1 ™ 1 1 Provincial Entomologist, 



Uom. Entomological Branch and 



Annapolis Royal, N. S. Truro, N. S. 



Since the discovery of Bordeaux mixture in the early 

 eighties of the last century, the question of the correct propor- 

 tion of lime to use in its manufacture has been much discussed. 

 In the early years of Bordeaux mixture many formulae contain- 

 ing various proportions of both lime and copper sulphate were 

 recommended. Finally, however, a mixture containing four 

 pounds of lime, four pounds of copper sulphate and 40 (Im- 

 perial) gallons of water — the so-called "4-4-40" formula- 

 came to be regarded as the standard mixture, and has largely 

 remained so. Some authorities, however, advocate a formu- 

 la containing just sufficient lime to neutralize the copper sul- 

 phate, while in recent months there has come into use in Nova 

 Scotia a formula for orchard spraying requiring an excess of 

 lime over copper sulphate of at least three to one. 



A review of the somewhat extensive literature dealing with 

 the complicated chemical problems involved in a study of this 

 subject, or treating of the preparation, fungicidal and physiolo- 

 gical effects, etc. of Bordeaux mixture, is beyond the scope of 

 the present article. Interested in the. subject mainly from the 

 standpoint of a safe fungicidal "carrier" for insecticides, the 

 writers found it impossible to ignore these other phases of the 

 question. A short review of some of the more important con- 

 tributions to this subject is therefore included, as a necessary 

 preliminary to an intelligent understanding of the question 

 to be discussed. 



Chemists have generally been somewhat reluctant to un- 

 dertake a study of the actual composition of Bordeaux mix- 

 ture, owing apparently to the many difficulties which this pro- 

 blem presents. Millardet, the discoverer of Bordeaux mis- 

 ture, working in conjunction with his colleague Gayon, a chem- 

 ist, stated (1) that in spraying with Bordeaux mixture, the 

 copper, as deposited on the leaves, is in the form of copper hy- 

 droxide Cu (OH) 2 . This opinion appears to have been gen- 

 erally accepted until the publication of Pickering's papers 

 (4, 7 & 8) As a result of his experiments, Pickering advanced 

 the opinion that the addition of lime in the form of clear lime 



