A Study of Meadow-Crop Diseases in New York 



59 



lists many European countries and Siberia as being within the range 

 of its distribution, and says that it " is not at all uncommon " in England. 

 Estimates in the records of the Plant Disease Reporter vary from " injuring 

 75 per cent of the crop " in Vermont (Haskell, 1919:156) to " 1 per cent 

 injury was estimated" in Delaware (Johnson and Haskell, 1920:73). 

 It has been reported as " one of the most common leaf spots " in North 

 Carolina (Stakman, 1922). Possibly a quotation from Tehon of Illinois 

 will indicate sufficiently well the probable situation with regard to the 

 disease on alsike clover in New York (Haskell and Wood, 1923 : 255) : 



It is a matter of interest to me to find that in the western part of Illinois .... the 

 white clover used largely for pasture purposes is covered with the mold. . . . Practically 

 all pastures where this clover is grown are infested. The infection of plants varies from 30 

 to 70 per cent and from 60 to 70 per cent of the leaves on these plants are affected with a 

 reduction of photosynthetic surface of 2 to 30 per cent. 



Killian (1923) maintains that when white clover is attacked only lightly, 

 the malady is somewhat beneficial because the tissue tends to remain 

 green longer. He assumes, of course, in this case that the green tissues 

 function normally, but this is unproved. 



Symptomatology 



Both dorsal and ventral aspects of diseased leaves of white clover are 

 shown in figure 13. The first signs are minute black pimples which 

 enlarge more or less circularly on the under leaf surface until a vein is 



Figure 13. lesions caused by dothidklla tkifolii on leaves of white clover 



