Dried powders of velvetbean and pine bark added to soil reduce Rhizoctonia solani-induced disease on soybean

Abstract

Diseases induced by Rhizoctonia solani, like damping-off and root and stem rot on soybean (Glycine max), are a serious problem around the world. The addition of some organic material to soil is an alternative control for these diseases. In this study, benzaldehyde and dried powders of kudzu (Pueraria lobata), velvetbean or mucuna (Mucuna deeringiana), and pine bark (Pinus spp.) were used in an attempt to improve soybean plant growth and to reduce the disease R. solani (AG-4) causes on soybean. Benzaldehyde (0.1-0.4 mL/kg of soil) and velvetbean (25-100 g/kg) significantly (P ≤ 0.05) reduced mycelial growth of R. solani in laboratory tests. In greenhouse experiments, the percentage of non-diseased plants was higher in treatments with pine bark and velvetbean (50-100 g/kg). In soil treated with kudzu (r 2 =0.91) or velvetbean (r 2 =0.94), increasing rates of these amendments tended to increase plant fresh mass. In microplot field conditions, soil amended with velvetbean (r 2 =0.85) and pine-bark (r 2 =0.61) significantly reduced disease on soybean. Numbers of Bacillus megaterium (r 2 =0.87) and Trichoderma hamatum (r 2 =0.92) and hydrolysis of fluorescein diacetate (r 2 =0.91) were higher in soil amended with increasing rates of velvetbean, indicating an increase in microbial activity. From this study it is concluded that dried powders of velvetbean and pine bark added to soil can reduce Rhizoctonia-induced disease on soybean.Additional keywords: Glycine max, Mucuna deeringiana, damping-off, microbial activity. RESUMOPós secos de mucuna e casca de pinus adicionados ao solo reduzem a doença causada por Rhizoctonia solani em soja.As doenças em soja (Glycine max) causadas por Rhizoctonia solani são um sério problema ao redor do mundo. A incorporação ao solo de resíduos orgânicos é uma alternativa para o controle destas doenças. Neste estudo, benzaldeido e pós-secos de kudzu (Pueraria lobata), mucuna (Mucuna deeringiana) e casca de pinus (Pinus spp.) foram usados com o objetivo de melhorar o crescimento de plantas de soja e de diminuir a doença causada por R. solani (AG-4). Benzaldehyde (0,1-0,4 mL/kg de solo) e mucuna (25-100 g/kg) reduziram significativamente (P ≤ 0.05) o crescimento micelial de R. solani em experimentos de laboratório. Em experimentos conduzidos em casa de vegetação a porcentagem de plantas sobreviventes foi maior em solo com casca de pinus e mucuna (50-100 g/kg

Diseases of Edible Oilseed Crops

“…Certain organic soil amendments may have similar effects as an approach for indirect biological control through cultural practices. For example, dried powders of velvet bean and pine bark added to the soil at the rate of 50-100 g/kg of soil can reduce R. solani-induced damping-off and root and stem rot disease in soybean (Blum and Rodriguez-Kabana 2006a). Seed treatment with alum recorded maximum seed germination, root length, shoot length, and seedling vigor index (Chandrasekaran et al 2000a,b).…”