Aphanomyces Cladogamus Drech., a Cause of Damping-Off in Peppers and Certain Other Vegetables

A species of Aphanomyces was isolated from damped-off pepper seedlings which had been grown in a sandy loam compost soil under glass. This fungus was obtained from up to 8% of the damped-off pepper seedlings. The morphological characteristics of this fungus corresponded so closely with the descriptions of Aphanomyces cladogamus Drech., which Drechsler isolated from diseased tomato rootlets, that the two fungi are considered to be the same. Reduction in stands of pepper seedlings resulted from both pre-emergence and post-emergence damping-off, when seeds were planted in soil inoculated with isolates of the fungus. Characteristic symptoms of postemergence attacks consisted of black lesions on the hypocotyl frequently extending into the bases of the cotyledons, and death of affected seedlings usually occurred. A. cladogamus was found to cause a considerable amount of damping-off in tomato, eggplant, radish, and spinach as well as in pepper. It attacked Spanish onions only slightly, but lettuce, pea, and muskmelon not at all. Except in spinach, A. cladogamus showed little tendency to colonize root tissues, whereas hypocotyl and cotyledonary tissues were highly vulnerable.