EFFECT OF HCN GAS AFTER COPPER FUNGICIDES 9 



Dry Bordeaux Substitutes 



In Tables 3 and 5 are presented the results of the use of HCN gas on cucumber 

 plants previously sprayed with proprietary Bordeaux powders. These sprays 

 were prepared to contain the same amount of copper that is present in 4 pounds 

 of crystalline copper sulfate in 50 gallons of Bordeaux. The Dow and Rex brands 

 of Bordeaux powders are slightly alkaline. The Corona, Riches Piver, Grasselli, 

 and Bowker brands are more strongly alkaline to litmus. In every case severe 

 injury occurred after the sprayed plants were gassed. This fact, however, is not 

 to be construed as casting any reflection upon these materials as fungicides when 

 used in the absence of gas. The reaction of these sprays within the limits shown 

 by a litmus paper test was not a factor in influencing the degree of injury. 



Table 3. The Effect on Cucumber Plants of HCN Gas Following 



Treatments with Certain Proprietary Copper Fungicides, and 



Determinations of Soluble Copper in the Residue. 



•trace of soluble copper in three cases; none m one. 



^Trace of soluble copper in five cases; none in two. 



'Only slightly alkaline. 



^Slight trace of soluble copper in one case. 



^Trace of injury in one case; none in three. 



'Soluble copper in two cases; none in one 



'Trace of soluble copper in one case; none in one. 



