Abstract
Efficacy of validamycin A (VM-A) for several sclerotial diseases was studied in vitro and in vivo. These diseases were caused by several sclerotial fungi such as Rhizoctonia solani I A, Rhizoctonia solani III B, Rhizoctonia oryzae, Sclerotium fumigatum, Sclerotium oryzae-sativae and Sclerotium hydrophilum. In vitro tests indicated that all these fungi were sensitive to VM-A and showed abnormalhyphal growth at 10 ppm VM-A after 1 to 2 days of incubation. Each sclerotial disease could be induced in rice plants by inoculation of mycelial blocks of each fungus at 26 to 32°C. In curative condition, VM-A (7.5 ppm) was effective for all sheath blight-like diseases except brown sclerotial disease by S. oryzae-sativae and brown sheath blight by R. solani III B, for which 60 ppm and 30 ppm VM-A were required, respectively. In protective condition 15-60 ppm was effective for these sclerotial diseases including rice sheath blight disease.
