Amaranthus spinosus, Leonotis nepetaefolia, and Leonurus sibiricus: New Hosts of Phomopsis spp. in Brazil. R. F. Cerkauskas, Former Graduate Research Assistant, Agriculture Canada, Vineland Research Station, Vineland Station, Ontario, Canada L0R 2E0. O. D. Dhingra, Professor, Departamento de Fitopatologia, Universidade de Viçosa, Viçosa, M. G. 36570, Brazil; J. B. Sinclair, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801; and G. Asmus, Graduate Research Assistant, Departamento de Fitopatologia, Universidade de Viçosa, Viçosa, M. G. 36570, Brazil. Plant Dis. 67:821-824. Accepted for publication 17 February 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-821.

Phomopsis spp. was isolated from Amaranthus spinosus, Leonotis nepetaefolia, and Leonurus sibiricus, common weeds in soybeans grown in southern Brazil. The latter two hosts were symptomless carries of Phomopsis spp. Pycnidia produced by cultures of Phomopsis spp. isolated from the three weed hosts gave rise to alpha and beta conidia typical of Diaporthe phaseolorum. The Phomopsis spp. isolates from L. nepetaefolia and L. sibiricus, but not from A. spinosus, reduced seed germination, radicle length, and emergence of UFV₁ soybeans but not of Rico 23 common bean (Phaseolus vulgaris) grown in infested sand and soil. These weed isolates colonized soybean stems and produced pycnidia. Isolates from A. spinosus did not produce pycnidia on common bean stems.