180 THE POTATO 



it may develop after the potato has been dug and 

 stored. Sometimes a large portion of the crop 

 is thus lost even after it has been harvested. 

 Thorough spraying of the vines will, at the same 

 time, impregnate the surface of the soil with the 

 copper-sulphate solution. Thus not only is the 

 formation of any considerable number of spores 

 prevented, but the spores that do happen to reach 

 the soil are destroyed. 



"It is believed that the spores of the fungus do 

 not live through the winter. If that be true the 

 mycelium of the fungus must either live over in 

 the dead tops that are left strewn about the field, 

 or else the tubers carry the disease over from one 

 season to the next. The latter is thought the more 

 probable, as it has been seen that the blighting of 

 the tops (if not checked by spraying) is very likely 

 to be followed by rot of the tubers, either before or 

 after digging. Of course, no one would think of 

 planting badly rotted potatoes, but those that are 

 but slightly affected may escape notice. These, if 

 planted, will be sufficient to start the infection the 

 next year, and once started it soon goes over the 

 field." 



This disease is very serious in Europe. In "Leaf- 

 let 23" of the Board of Agriculture and Fisheries of 

 Great Britain is the following: 



"This disease, well termed by agriculturists the 

 ' potato disease, ' has in the past been the cause of 

 immense loss, and is even at the present day the 

 chief trouble with which potato growers have to 

 contend. 



"The first sign of this disease is the presence of 

 yellowish spots on the leaves. These spots grad- 



