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Etiology of Atypical Symptoms of Charcoal Rot in Sunflower Plants Parasitized by Larvae of Cylindrocopturus adspersus. S. M. Yang, Research plant pathologist, USDA Conservation and Production Research Laboratory, Agricultural Research Service, P.O. Drawer 10, Bushland, TX 79012; Phytopathology 74:479-481. Accepted for publication 17 November 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/Phyto-74-479.

Sunflower plants (Helianthus annuus L.) parasitized by larvae of the sunflower stem weevil, Cylindrocopturus adspersus, developed black-to-brown discoloration of the stalks. Alternaria alternata, Fusarium roseum, F. solani, Macrophomina phaseolina, Phoma macdonaldii, and Rhizopus arrhizus were isolated from the discolored tissues of sunflower stalks parasitized by the larvae of C. adspersus as well as from the larval and adult weevils. Greenhouse-grown sunflower plants inoculated with one of five fungi, A. alternata, F. roseum, F. solani, P. macdonaldii, and R. arrhizus alone or in combination with M. phaseolina, developed black-to-brown discoloration. Sunflower plants, however, inoculated with M. phaseolina alone developed typical charcoal rot symptoms, a gray discoloration with many black sclerotia on the stalks. The results indicate that the five fungi are capable of contributing to the development of black-to-brown discoloration on sunflower stalks infected by M. phaseolina and parasitized by larvae of C. adspersus.