Abstract
A description is provided for Corticium rolfsii. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Arachis, Phaseolus and many other legumes, Beta, Brassica, Cannabis, Cinchona, Citrus, Cucumis, Ficus, Lycopersicon, Musa, Oryza, Solanum, Saccharum and a wide variety of other crops, ornamental plants and weeds. DISEASE: Stem rot, foot rot, crown rot, sclerotium wilt, blight. Infection commonly commences at about soil level and extends a few cm above and below. Epidermis, cortex and stele are all invaded; necrosis precedes penetration. GEOGRAPHICAL DISTRIBUTION: Widespread in moist tropics and warm temperate areas; present in most of Africa and southern Asia; Australasia; Spain, Italy and through central Europe to southern Sweden; North America (particularly important in southern USA), Central America and the West Indies and much of S. America (CMI Map 311, ed. 3, 1969). TRANSMISSION: A facultative parasite, capable of extensive saprophytic growth in surface layers of soil. Persists on crop residues and weed hosts. The sclerotia are disseminated by cultural practices, wind and water; a proportion survive passage through sheep and cattle. They occur as contaminants amongst seed and the fungus is occasionally seed-borne, e.g. in groundnut and watermelon, or present on vegetative propagation material. The perfect state is infrequent in the field and is probably not of primary importance in disease transmission.