Efficacy of Pepper Tree (Schinus molle) Extracts to Suppress Growth of Botrytis fabae and Manage Chocolate Spot Severity on Faba Bean (Vicia faba) at Sinana, Bale Zone, Southeastern Ethiopia

Abstract

Fungal phytopathogens cause considerable crop yield reduction if not managed well. Use of synthetic chemicals is a conventional method of managing plant pathogens. However, the negative environmental impact of using synthetic chemicals prompted the search for plant-based compounds, which are relatively safer to the environment than synthetic agro-chemicals. In this study, crude extracts of pepper tree (Schinus molle) were evaluated through in vitro and in vivo tests to suppress growth of Botrytis fabae and to manage chocolate spot of faba bean (Vicia faba L.), respectively. Growth inhibitory effects were evaluated by applying different concentrations of aqueous, methanol and ethanol leaf extracts of S. molle or extraction solvents (control) using agar diffusion method in the laboratory. The laboratory experiment was done in a completely randomized design with three replications. The efficacies of leaf extracts of S. molle were evaluated through in vivo test after spraying the extracts and scoring the disease incidence and severity on V. faba (variety Shallo) grown in the field right after the detection of disease symptoms at 61 day after planting (DAP) up to 89 DAP on a weekly basis. The design for the field experiment was randomized complete block design (RCBD) with three replications. Mancozeb 80WP was used as a check or control treatment. Results of the in vitro test showed that all extract types had antifungal properties and significantly reduced mycelial growth in a concentration-dependent manner. Growth inhibitory effects also varied with extraction solvent. Results of the in vivo experiment showed that disease severity was significantly reduced by all types of S. molle extracts and particularly that of methanolic extract was on a par with the synthetic fungicide, Mancozeb 80WP. Corresponding to reduced disease severity, extract application increased grain yield by ca. 38- 95% when compared with the negative control. Therefore, it could be concluded that, S. molle extracts can be considered as one of the alternative means of suppression of the negative effects of this fungus. However, screening of the active principle(s) of S. molle leaf extracts is subject to further research for effective utilization of this plant in crop protection.

Keywords: Disease incidence/severity, In vitro, In vivo, Plant extract, Schinus molle, Shallo, Vicia faba