POTATOES. 



263 



entire field may be killed in a very few days from the time the 

 disease is first noticed. In seasons not very favorable to it, the tops 

 maj^ die prematurely, but so g-raduallj' as to be mistaken for the 



Fig. 1. Late blight of potatoes in tlie early stages. Phytophthura infestana. 



natural maturing- of the plant. I think it most often acts in this 

 way in this state. From the tops, the spores may pass to the tubers, 

 where thej^ cause them to rot. 



This disease may be prevented by the use of Bordeaux mixture, to 

 which reference will be made further on. 



Figure 1 shows the way in which the disease often commences. It 

 frequently starts at some spot on the leaf which has been injured, 

 and from there spreads in every direction. This will many tiines be 

 noticed around holes made by beetles. 



EXPERIMENTS. 



This subject has attracted much attention from experimenters in 



the older states, where the use of Bordeaux mixture as a preventive 



has been so successful that it has become verj- generally adopted 



bj' the most progressive planters. The results are not always uni- 



