WEED HOSTS FOR RHIZOCTONIA-SOLANI, CAUSAL AGENT FOR RHIZOCTONIA FOLIAR BLIGHT OF SOYBEAN (GLYCINE-MAX)

Greenhouse studies were conducted to determine host status of weed spe cies for Rhizoctonia solani AG-1, which causes Rhizoctonia foliar blig ht of soybean. Weed species were barnyardgrass, broadleaf signalgrass, common cocklebur, entireleaf morningglory, hemp sesbania, itchgrass, johnsongrass, large crabgrass, northern jointvetch, prickly sida, purp le nutsedge, redweed, sicklepod, and smooth pigweed. Seedling weeds we re inoculated with suspensions containing intraspecific group IA and I B isolates of the fungus. In the first study, sclerotia of IA were rec overed from tissue of all weeds except smooth pigweed, and mycelia of IA were recovered from all except smooth pigweed and redweed. In that study, neither microsclerotia nor mycelia of IB were recovered from si cklepod, barnyardgrass, or large crabgrass, and only microsclerotia we re recovered from itchgrass and purple nutsedge. In the second study, sclerotia of IA, microsclerotia of IB, and mycelia of each isolate wer e recovered from all weed species. In other studies, R. solani spread from at least six of seven weed species to a noninfected soybean plant growing in close proximity. These studies emphasize the importance of weed control, not only for reducing plant competition and increasing yield, but also for the potential impact on development of RFB.