Evaluation of certain fungicides for the control of tar spot disease of water yam (Dioscorea alata L.) in Ghana

Abstract

Tar spot disease of water yam (Dioscorea alala L.) is widespread in all yam growing regions of Gbana. Although it does not usually cause more than 30 per cent loss in yield, it has the potential and has been observed to cause complete crop failure under favourable conditions. The present study evaluated the favourable conditions as well as the effectiveness of fungicides in controlling the disease. Ben/ate, Dithane M-45 and Polyram-Combi at the rates of 1.0, 1. 5 and l. 5 gil of water respectively either totally or almost completely controlled the disease when aerial parts of the vines were sprayed weekly or bi-weekly. Benlate was the most efficient, followed by Dithane M-45 and then Polyram-Combi. Tbere were no significant differences in disease severity between plants sprayed weekly and hi-weekly. The use of Benlate, Dithane M-4S and Polyram-Combi increased yield by 63.0, 47.0 and 27.0 per cent respectively. It is suggested that a biweekly spraying programme should be followed to control tar spot disease of water yam.