Etiology of a Late Season Wilt in Helianthus annuus. M. L. Richeson, Assistant Professor of Biological Sciences, Indiana University-Purdue University, Fort Wayne 46805. Plant Dis. 65:1019-1021. Accepted for publication 28 September 1981. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-1019.

Two types of bacteria and a fungus were isolated from lesions on Helianthus annuus showing wilt symptoms. One bacterial isolate was Erwinia carotovora var. carotovora, the other Xanthomonas campestris. The morphology of the fungus was similar to that of Cephalosporium. Suspensions of spores or cells of the isolates were used to inoculate seeds, seedlings, and growing plants at 2-wk intervals until head set. Healthy young plants were resistant to the isolates. As plants matured, they became more susceptible to E. carotovora and Cephalosporium, which may produce necrosis on the stems and consequently weaken them. Xanthomonas appeared to be opportunistic, acting secondarily to contribute to the wilt syndrome.