Evaluation of vermicompost doses for management of root-rot disease complex in Coleus forskohlii under organic field conditions

Organic field experiments were conducted (2007-09) for the medicinal plant Coleus forskohlii with different doses of vermicompost to minimize the root-rot disease incidence and increase the growth and yield. The use of vermicompost significantly increased the growth parameters in general but the maximum plant height, plant spread and number of branches increased with the application of 5 t ha(-1) of vermicompost. Root-rot/wilt, a complex disease of C. forskohlii involving Fusarium chlamydosporum and Ralstonia solanacearum, was significantly (P < 0.05) reduced in terms of percent wilt incidence (PWI) and severity of root-rot as measured by percent disease index (PDI) with different doses of vermicompost. The highest levels of biomass (root and shoot; 48 % and 71 %, respectively) and forskolin yield (46 %) and disease suppression (PWI and PDI; 73 % and 82 %, respectively) were found at the top level of vermicompost (5 t ha(-1)). Nutrient (NPK) uptake was significantly elevated in plots supplemented with vermicompost compared to control plots.