Improving the efficacy of Tithonia diversifolia extract in management of foliar diseases of sesame intercropped with maize under tropical conditions

Abstract

Abstract Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) diseases are major constraints to sesame production. Although disease management through intercropping of sesame with maize and foliar-spray with extracts of Tithonia diversifolia have been found to be effective, the frequency of application of the extracts required to achieve optimal disease control have not been determined. Therefore, a study was carried out to determine the effect of frequency of application of T. diversifolia extract on CLS and ALB diseases of sesame intercropped with maize during the early (June – September) and late (August – November) cropping seasons of 2011. Field experiments laid out in a Randomised Complete Block design and in a split plot arrangement with three replications were conducted in Ejigbo, Nigeria. Treatments consisted of aqueous Tithonia diversifolia leaf extract applied at 7.0, 7.5 or 8.0 % (w/v) in one-, two- or three- spray regimes at 2-week intervals from three weeks after planting (WAP) to plots of sesame intercropped with maize; Unsprayed sesame/maize intercrop; sesame/maize intercrop sprayed with Carbendazim (50 %)WP and unsprayed sole sesame plots. Results revealed that CLS and ALB incidence, severity and defoliation were significantly (p < 0.05) reduced by three-spray regime of 7.5 % (w/v) T. diversifolia extract. The efficacy of 7.5 % (w/v) T. diversifolia extract was comparable to that of 8.0 % (w/v) T. diversifolia extract or synthetic fungicide (Carbendazim 50 %WP). This study showed that the three-spray regime of 7.5 % w/v T. diversifolia leaf extract is sufficient to control foliar diseases of sesame intercropped with maize.