202 A Capper Emalsion as a Fmigicide 



Delailed observations of Experiment II. 



Inoculated August 16 



August 20 



August 23 



August 28 



Sept. 11 



(terminal leaflet 



. -left 

 sprayed \^^^^^^ 



Leaf a 



no diseased spots no diseased spots ) -.xn. i i r 

 do. do. ' do. do. IhVholeleaf 



uninjured 



do. 



do. 



do. 



do. 



Leaf b 

 unsprayed 



T r r terminal 

 Leafc Ijpf^ 



sprayed (^j^j^^ 



1 distinct spot of 1 spot 1 cm., another 

 blight I 0-3 cm. diam. 



2 distinct spots of The two spots have 

 blight \ coalesced 



4 distinct spots of Whole leaflet blackened 

 blight and withered 



All three leaflets ' Whole leaf 



destroyed 



destroyed 



no diseased spots 

 do. do. 



do. do. 



no diseased spots 

 do. do. 



do. do. 



no spots 

 do. 



do. 



no spots 

 do. 

 do. 



On the same date as the last experiment, a plant with many badly 

 diseased leaves was sprayed with the emulsion but the disease extended 

 in all the affected leaflets. 



From these experiments, it is evident that the emulsion acted as a 

 preventive against infection by zoospores of PhytophtJiora infestans and 

 justified trials on a larger scale. 



Later in the year, two small plots of potatoes, each measuring 

 approximately 120 scj. yds, were sprayed with the emulsion and on this 

 occasion when tap water was used instead of distilled water hitherto 

 employed in these experiments, a little difficulty was experienced in 

 spraying the fluid owing to the accumulation in the nozzles of the 

 sprayer of the green sticky substance referred to already. 



At the time the crop was lifted the leaves of the sprayed plots were 

 certainly much greener and showed far less damage by blight than those 

 of the unsprayed control plot, but owing to the lateness of the appear- 

 ance of the blight, all three plots had approximately the same low 

 percentage of diseased tubers although the two sprayed plots showed 

 a slightly greater total yield than the control plot. 



In 1918, these trials were repeated and two more small plots, each 

 approximately 36 sq. yds in area, were sprayed, the control plot of the 

 same size being between them. On Plot I, the emulsion descril)ed 

 {i.e. containing the equivalent of 0-4 per cent. CUSO4 . SH.^O and 2 per 

 cent, soft soap) was sprayed. On Plot HI, an emulsion containing twice 

 as much copper and twice as much soap was used. The plots were 

 sprayed on August 7. Each plot received six gallons, applied by means 



