H. WORMALD AND L. K. WORMALD 203 



of a knapsack sprayer, and both emulsions were made with rain water 

 and were applied in the usual way by a man accustomed to the work, 

 but no unusual care was taken to effect complete treatment of the 

 plot. 



To make six gallons of emulsion for Plot I, three gallons of soap 

 solution containing 1-2 lbs. (544-3 gms.) of soap were put in a perfectly 

 clean wooden pail; 0-24 lb. (]08'9 gms.) of copper sulphate was dis- 

 solved in three gallons of water and this solution was addsd slowly to 

 the soap solution, which was stirred well all the time. 



On August 19, both plots were sprayed again^ each receiving six 

 gallons as before. On this occasion both emulsions were made with 

 tap water and Plot I was actually sprayed with emulsion made from 

 tap water though a small amount of a putty-like substance was formed; 

 this remained in the strainer and the whole of the spray went on satis- 

 factorily. In the case of the stronger emulsion, a mass of green "putty" 

 was formed, clogging up the tube and nozzles of the sprayer, even after 

 straining, which was a very long process; this was therefore rejected, 

 the sprayer thoroughly cleaned and the emulsion made again with rain 

 water. Although some '"putty" was formed, the emulsion which was 

 put on Plot III contained considerably more copper than that put on 

 Plot I. 



The green putty-like substance has strongly adhesive properties and 

 some method has yet to be found for retaining all the copper in the 

 emulsified condition. 



The effect of the spiay on the leaves was most striking. The control 

 plot began to blacken about three weeks before the sprayed plot showed 

 any signs of being affected and on September 25, when the sprayed 

 plots were still fairly green and healthy, not one green leaf could be 

 seen on the control plot. 



From the results given, it will be seen that the sprayed plots gave 

 an appreciably higher yield than the unsprayed and the percentage of 

 diseased tubers was much higher in the unsprayed plot than in either 

 of the sprayed plots. 



Plot I. Sprayed twice with an emulsion containing approximately 

 the equivalent of 0-4 per cent. CUSO4 . 5H2O. 



Total 89 



