ROOT AND STALK ROT OF FIELD CORN IN SOUTHWESTERN ONTARIO: II. DEVELOPMENT OF THE DISEASE AND ISOLATION OF ORGANISMS

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Abstract
The development of root and stalk rot in two corn inbreds was followed in 1956 and isolations were made of organisms associated with the disease. Infection of the root tips early in the life of the plants was followed by progressive colonization of the roots as the plants aged and by rotting of the stalks at maturity. Isolations showed that numerous organisms (Fusarium oxysporum, F. maniliforme, F. equesiti, F. sp., Pyrenochaeta terrestris, Trichoderma spp. and Alternaria sp.) were associated with the rotting of the roots but that only F. oxysporum and Trichoderma spp. were obtainable from the stalks of diseased plants. The two latter organisms entered the stalks through diseased adventitious roots or mesocotyls and were considered to be the cause of the disease in 1956. The association of other organisms in this complex disease in other years is discussed.