THE ACTION OB^ BOKDEAUX MIXTURE 

 ON PLANTS. 



By B. T. p. barker, M.A., and C. T. GIMINGHAM, F.I.C. 



(University of Bristol ; Agricultural and Horticultural 

 Research Station.) 



In the course of experimental work involved in the investigation 

 of the fungicidal action of Bordeaux mixture^, a number of observations 

 have been made on the inter-action between the spray fluid and the 

 plants with which it comes into contact in the process of spraying. 

 Further attention has now been given to this part of the subject and as 

 the results help to explain various points arising in practical spraying, 

 it is proposed to give an account of the experiments here. 



It will be most convenient to consider the work in two sections, 

 dealing with (a) spray injury or " scorching " by Bordeaux mixtures, 

 and (6) the penetration of copper from Bordeaux mixtures into the plant. 



Foliage Injury or Scorching by Bordeaux mixture. 



The injury to foliage, more or less pronounced, which is frequently 

 found to follow the application of Bordeaux mixture, has been the subject 

 of a good deal of work, especially in America. As regards its possible 

 bearing on the question of the fungicidal action of Bordeaux mixtures, 

 the matter is discussed shortly in Section II of the second paper 

 referred to. In considering the various means by which copper might 

 be brought into solution on the surface of sprayed leaves, the suggestion 

 was then made that some importance should be attributed to the in- 

 fluence of exudations from injuries to the leaves ; and it was further 

 suggested that if soluble copper is produced in this way, it would probably 

 show its presence by causing or intensifying scorching. This point has 

 been followed up in some detail. 



In order to have reliable material for experimental work in this 



> See Jmirn. Agric. Sci. iv, p. 09 ; ihid. iv, p 7G. 



