



The influence of calcium upon the toxicity of copper 

 is of interest on the problem of fungicides and fungicidal 

 action. From the results abtained in the experiments des- 

 cribed above the conclusion seems warranted that only a 

 small portion of the soluble copper in Bordeaux mixture is 

 effective as a fungicide. Yet it is a well known fact that 

 a long list of fungous diseases including apple bitter-rot 

 can be controlled by the proper applications of Eordeaiix 

 mixture to the host plants. The use of KOH instead of Ca(0H)2 

 in preparing the fungicide should result in a much more toxic 

 mixture, for, as brought out in the preceeding experiments, 

 potassium is only about one fourth as effective as calcium 

 in decreasing the toxicity of copper. From the standpoint of 

 the host, however, it is quite probable that this anti-toxic 

 effect of the calcium is important in preventing "spray- 

 injury " to the foliage and fruit while the small amount of 

 soluble copper present is, in most cases, sufficient to 

 prevent fungous growth. 



