Efficacy Of Leonotis Nepetifolia L. And Ocimum Gratissimum L. Extracts In Controlling Ascochyta Blight (Phoma Exigua) Of French Bean (Phaseolus Vulgaris L.)

French bean (Phaseolus vulgaris L.) is an important export vegetable crop that faces serious production challenge due to Ascochyta blight (Phoma exigua). The objectives of this studywere to determine the; (i) antifungal activities of methanol extract of Leonotis nepetifolia and  Ocimum gratissimum against Phoma exigua in vitro, (ii) fungicidal effects of extracts of the two test plants on the incidence and severity of Ascochyta blight, and yield of French bean. Methanol extracts of composite leaves and tender stems of each test plant were diluted to obtain final concentrations of 40.0, 20.0, 10.0, 5.0, 2.5, 1.25, 0.63, 0.31, and 0.16 mg ml-1 (w/v) for use in antifungal tests. The pathogen was isolated from infected French bean pods and used for inoculation in greenhouse and field experiments. Laboratory bioassays were conducted using Kirby-Bauer disc diffusion method in a completely randomised design in triplicate. The diameters of zones of inhibition and the minimum inhibitory concentrations of the methanol extracts against the pathogen were determined. The in vivo experiments were conducted at Egerton University and Kenya Agricultural and Livestock Research Organization – Njorofields. The experiments were laid in a 2 × 6 factorial arrangement of randomized complete  block design with three replicates. Methanol extracts of O. gratissimum and L. nepetifolia at 20.0, 10.0, 5.0, 2.5 and 1.25 mg ml-1 were sprayed per plot at 14 days after emergence (DAE). The in vivo data were collected on disease incidence and severity, yield; and percent disease index (PDI) and disease severity index (DSI) determined per plot.