General Diseases 23 



pected upon almost any species of plant, so wide is its range 

 of hosts. 



Soil disinfection (p. 460), when practicable, may be em- 

 ployed; otherwise general sanitary measures, destruction of 

 Jjifective refuse, and the use of resistant plants are remedial. 

 (7/ Southern-blight^^ (Sclerotium rolfsii Sacc). — Plants af- 

 fected with this disease lose color, wilt, and may die. The 

 fungus is found, usually, around the base of the stem or on 

 the roots, producing lesions of rot, a dense white mycelial 

 mat, and large numbers of spherical, yellow sclerotia, closely 

 resembling mustard seeds, which are diagnostic. The causal 

 fungus may be recognized upon numerous hosts particularly 

 in the Southern states, and as far north, at least, as central 

 Illinois. It has been identified upon tomato, eggplant, Irish 

 potato, sweet potato, beet, peanut, pepper, cauliflower, 

 bean, cowpea, cabbage, carrot, squash, muskmelon, water- 

 melon, rhubarb, fig, cotton, violet, hydrangea, daphne, 

 chrysanthemum, pinks, bellflower, morning-glory, Japanese 

 fiber-plant, grasses, sugar cane, and several weeds and may 

 be looked for on any plant. Treatment is the same as for 

 stem-rot. • 



Texas root-rot ^^'^ ^" (Ozonium omnivorum Sh.).* — ^ Most 

 destructive to cotton (see p. 346) this disease affects a very 

 wide range of plants in Texas, California, Oklahoma, New 

 Mexico, and Arizona. It has been noted upon nursery 

 stock, apple, mulberry, chinaberry, hnden, ash, quince, locust, 

 Prunus, hibiscus, persimmon, elm, lime, maple, beet, peanut, 

 bean and various legumes, flax, cotton, sweet potato, Sida, 

 ragweed, cocklebur, alfalfa, and several other plants. The 

 chief characteristics are a sudden wilting or dying of the 

 diseased plant, or if the main root is not completely diseased 

 merely a slight yellowing and unhealthy appearance. The 

 roots of plants that have recently died are closely invested 

 with a cinnamon-buff felt of hyphae, in which strands are 

 conspicuous. Treatment is as for stem-rot. 



* Duggar believes the conidial stage to be Phymaiotrichum omnivorum 

 (Sh.) Dug." 



