Forage Crops 323 



conditions does more damage than leaf-spot. The spot 

 produced is deep yellow, verging to orange, and bears nu- 

 merous orange-colored pycnidia. The fungus winters on 

 infected leaves. Early cutting is beneficial. 



Wilt ^"'^ {Sclerofinia trifoUorum Eriks.). — This wilt, which 

 in some respects resembles lettuce drop, has been noted on 

 alfalfa and the clovers, red, white, crimson, bastard, mam- 

 moth, and alsike, in several widely separated sections of the 

 United States and Europe. 



It kills the plants, and under favorable weather conditions, 

 the chief factor of which is a humid atmosphere, it may ex- 

 tend from plant to plant and involve large areas in the field. 



Plants may show a variety of symptoms. Sometimes the 

 leaves droop, and become matted together in a sodden mass 

 at the base of the plant, and overgrown with a white cotton- 

 like layer of mycelium, in which black sclerotia, similar to 

 those described under lettuce, are found. At other times the 

 stems may be the point of attack, showing dead, brown sec- 

 tions covered with the mycelium and bearing sclerotia. 

 Upon splitting a stem open the central part may be found 

 filled with mj^celium and with occasional sclerotia about the 

 size of a grain of wheat. The white mycelium and black 

 sclerotia are absolutely diagnostic. 



Under unfavorable weather conditions the disease may 

 die out and fail to reappear, but if the weather is favorable 

 to this fungus, the wilt may reappear year after year with 

 increased severity, involving larger and larger areas. 



Stewart, French, and Wilson reported large areas where 

 50 per cent of the stalks were killed, though later the field 

 recovered entirely. 



Where the disease is troublesome, rotation of crops and 

 deep plowing to bury the sclerotia seem to be the only re- 

 course. Isolated, infested areas may be cleaned out by burn- 

 ing. 



Texas root-rot ^^'^^ (Ozonium). — This rot is a soil disease, 

 which in its general characters is identical with that so 

 disastrous upon cotton and the treatment applied to cotton 



