New York Agricfltfral Experiment Station. 181 



caused by the fungus Phytophthora infestans, which is the chief 

 concern of potato growers in this connection and it is with this 

 disease that the present bulletin has to do. 



Although considerable has been written upon the subject it seems 

 unnecessary to give a detailed review of the literature here. It is 

 sufficient, perhaps, to say that while evidence both for and against 

 the persistence of Phytophthora has been produced the view that 

 it does not persist has been the prevailing one. However, Massee, 

 an English mycologist, makes the following remarkable statement: 1 

 " I have observed the important fact that, when diseased potatoes 

 are planted, after the crop has been lifted, the remains of the old 

 seed potatoes, when brought to the surface of the ground, will pro- 

 duce a crop of the fungus bearing myriads of spores. If such old 

 seed potatoes are kept buried in soil until the following year, and 

 then exposed to light under favorable conditions, fungus fruit is still 

 produced, and continues to grow so long as a scrap of the old potato 

 remains. I have now in the laboratory at Kew gardens scraps of 

 last year's seed potatoes covered with the fungus, and with the 

 spores thus produced have successfully inoculated the leaves of 

 young potato plants. * * * * In all probability the fungus is 

 always present in land where potatoes are grown at short intervals." 

 Massee even goes so far as to recommend gathering and destroying 

 the diseased tubers as a means of controlling the disease. Clinton, 

 who made field studies in Connecticut, says: 2 " We do not wish to 

 state positively, from these observations, that the blight starts 

 earlier and more vigorously in a field that bore a blight-diseased 

 crop the year before, as such factors as situation of the land, earliness 

 of planting, etc., may need consideration here, but so far as they go 

 they seem to point to this conclusion." Clinton's subsequent dis- 

 covery of the resting spores (oospores) of the blight fungus 3 tends to 

 support the theory that the fungus may persist in the soil, but it is 

 still unknown how frequently oospores are formed in nature or what 

 part they play in primary infection. 



^lassee, George. Some diseases of the potato. Jour. Roy. Hort. Soc. 19 : 139. 

 1904. 



2 Clinton, G. P. Report of the Botanist. Conn. Sta. Rpt. for the Year 1905, 

 Part 5, p. 311. 1906. 



3 Clinton, G. P. Oospores of potato blight. Science 33: 744-747. 12 May, 1911. 

 Ibid. Oospores of potato blight, Phytophthora infestans. Conn. Sta. Rpt. for 



1909 and 1910. Part 10, pp. 753-774. Je., 1911. 



