14 James G. Horsfall 



mold of stems caused by Botrytis sp.; on alsike clover: * Stagonospora leaf 

 spot, Pseudopeziza leaf spot, and powdery mildew; on white clover: 

 * Pseudopeziza leaf spot, * bacterial leaf spot, * powdery mildew, and 

 mosaic; on alfalfa: yellows, downy mildew, walnut antagonism, Cercospora 

 leaf spot, * Pseudoplea leaf spot, * Macrosporium leaf spot, and * girdle ; 

 on sweet clover: Cercospora leaf spot, Stagonospora leaf spot, * girdle, 

 and mosaic : on vetch : Botrytis sp. (causing a leaf spot) ; on hop clover : 

 Cercospora leaf spot; on yellow trefoil: * Cercospora leaf spot, * Stagono- 

 spora leaf spot, * Pseudoplea leaf spot, and Pseudopeziza leaf spot; on 

 timothy: rust and Cladosporium graminum; on red top: * Cercospora leaf 

 spot, Helminthosporium triseptatum, and stem rust; on quack grass (a 

 meadow crop by courtesy) : Phyllachora graminis, stem rust, Pyrenophora 

 tritici-repentis (ascospore and conidial stages), * Septoria agropyri, and 

 Urocystis agropyri; on foxtail: Piricularia leaf spot and head smut; on 

 orchard grass: stem rust and leaf smut; on blue-grass: powdery mildew 

 and leaf rust. 



DISCUSSION OF SPECIFIC DISEASES 



The diseases discussed were studied with the following points in mind: 

 (1) to find diagnostic characters for separating them; (2) to unravel the 

 nomenclatorial tangles encountered; (3) to study the life history of the 

 pathogene through field work, pure cultures and inoculations; (4) to study 

 the factors affecting incubation and infection; and (5) to determine the 

 sensitivity of the causal organisms to various dust fungicides, by tests 

 in the laboratory, greenhouse, and field. A discussion of the importance of 

 each disease in the State is usually omitted, because this is indicated in 

 tables 3 and 4. Some information gleaned from the literature on this 

 point, however, is given in certain instances for comparison. • 



DISEASES OF LEGUMES 

 MACROSPORIUM LEAF SPOT 



Suscepts 



No suscept other than red clover has been found naturally affected 

 by Macrosporium leaf spot in New York, but alsike, white clover, alfalfa, 

 and sweet clover have been successfully inoculated by the writer and the 

 pathogene has been reisolated. These plants showed fewer and much 

 smaller spots than those on the red clover inoculated at the same time, 

 indicating that they are less susceptible. Krakover's (1917:289) negative 

 results from inoculation trials upon alsike clover, crimson clover, white 

 clover, and alfalfa may indicate pathogenic differences among various 

 strains of the causal organism. Alsike clover has been reported as diseased 



