398 FORAGE PLANTS AND THEIR CULTURE 



From these figures, clover hay should consist of about 

 60 per cent stems, 30 per cent leaves and 10 per cent 

 flower heads. 



470. Diseases. Red clover is subject to a long list 

 of fungous diseases, few of which are, however, a serious 

 menace to its culture. Only the more important and more 

 common ones are here mentioned. 



The leaves may be affected by clover leaf-spot (Pseu- 

 dopeziza trifolii) ; black spot (Polythrincium trifolii) ; 

 powdery mildew (Erysiphe polygoni) ; downy mildew 

 (Peronospora trifoliorum) ; and clover rust ( Uromyces 

 striatus). It is rare that any of these diseases causes much 

 damage. 



The roots are subject to a root rot (Rhizoctonia violacea). 



The stems are sometimes injured by stem rot (Sclero- 

 tinia trifoliorum) which is easily recognizable by the large 

 dark sclerotia formed. Clover anthracnose (Colleto- 

 trichum trifolii) is probably the most destructive disease 

 that has attacked red clover in America. It appears as 

 purplish spots on the stem which increase in size until the 

 stem is girdled and thus killed. It is known to occur in 

 Maryland, Virginia, Ohio, Tennessee and Alabama, and 

 is probably much more widely spread. No direct means 

 of control is known, but results secured at the Tennessee 

 Experiment Station show that highly resistant strains 

 may be secured by selection. 



Two other anthracnoses, caused respectively by Colle- 

 totrichum cereale and Gloeosporium trifolii, are also found 

 occasionally, but no serious damage by either has been 

 reported. 



471. Clover sickness. This term is used to designate 

 a condition or conditions which prevent the successful 

 growing of red clover, at least continuously. This has 



