THE POTATO IN BRITISH COLUMBIA. 



67 



1. A typical leaf-roll plant (photo 

 by P. Murphy). 



their harsh, brittle texture. Plants of such varieties as Green Mountain assume a 

 low-headed, bushy appearance when infected with leaf-roll, while those of the Irish 

 Cobbler type assume a stiff, upright appearance. Another good diagnostic character 

 is the low yield and close attachment of the potatoes in clusters to the stem. There 

 is no sign of disease on or within the tubers, and for this reason potatoes from 

 leaf-roll plants will likely be planted by one who is inexperienced at identifying 

 a leaf-roll plant during the growing season. 



Leaf-roll may be first detected when the plants are from 5 to 8 weeks old, and 

 if there are no evidences of leaf-roll when the plants are 9 weeks old the disease 

 will probably not develop later. 



No casual organism has yet been isolated in connection with this disease, and 



Fl- 



it on the left affected with leaf-roll ; that o 

 (photo by P. Murphy). 



healthy 



