Antifungal potentials of aqueous extracts of selected indigenous flora against leaf and stem blight (Alternaria bataticola) disease of sweet potato

Abstract

Leaf and stem blight (Alternaria bataticola) is one of the principal constraints to effective sweet potato production in many parts of the tropics. This work assessed the potentials of extracts of some indigenous plants to control the disease in vitro and under field conditions. The treatments comprised 20% aqueous extracts of Stachyterpheta jamaicensis, Cyathula prostrata, Diodia scandens, Ageratum conyzoides and Hyptis suaveolens, mancozeb and water (control). The experiment was set up in RCBD with 3 replicates. The results showed that all the extracts inhibited spore germination (65.08-78.71%) and radial growth (77.54-92.01%) of the pathogen in vitro, though these were statistically inferior (P>0.05) to 82.06 and 95.25% recorded for mancozeb respectively. The extracts of the indigenous flora also performed well in inhibiting the disease in vivo. Mancozeb gave the highest reduction of blight incidence (18.92%) and severity (1.18) on the treated crop, however the values (20.11-30.06%) and 1.24-2.79) of the indigenous flora extracts were significantly (P<0.05) superior to the control which had 81.35% and 7.47 for the respective test parameters. The high minimization of disease incidence and severity in mancozeb and extracts treated plots compared to the control may have accounted for the higher yield of root (6.07-10.65 tha-1) and haulm (1.37-2.51 tha-1) than (3.01 tha-1 and 0.87 tha-1) obtained for the control respectively. This study showed that smallholder farmers of sweet potato can use aqueous extracts of S. jamaicensis, C. prostrata and H. suaveolens to keep leaf and stem blight at bay and increase the productivity of the crop.