A NEW WILT DISEASE OF ACACIA NILOTICA CAUSED BY FUSARJUM OXYSPORUM

Abstract

This paper reports a new vascular wilt disease of Acacia nilotica seedlings caused by Fusarium oxysporum. The affected seedlings exhibited varied symptoms such as drooping of leaves at the tip or side twigs, top dying, mortality and in some cases recovery in the form of new shoots. Browning of vascular tissue and clogging of xylem vessels by mycelium and spores of fungus as well as gums were associated with diseased plants. The disease caused more mortality in seedlings raised in polythene bags (33.7%) than those in root trainers (16.9%). The source of infection was found to be soil borne and not seed borne. The pathogenicity of F. oxysporum was confirmed in the laboratory by artificial inoculation. Of the seven fungicides tested, Bavistin and Benlate inhibited pathogen growth completely in culture at 0.1% concentration. Soil drenching with Thiram (0.05%), followed by seed dressing with Bavistin (0.05%), gave the best growth performance of seedlings as well as inhibition of disease in root trainers.