Effectiveness of Alternative Control Methods for Tithonia diversifolia on Water Yam (Dioscorea alata) Plot

Tithonia diversifolia has become a significant agronomic problem to optimum arable crop production in Nigeria which has necessitated effective and timely control if the good yield is expected on infested soil. This study compared the performance of water yam under different weed control methods on Tithonia infested plot at Ogunba village near Baaya-Oje in Surulere Local Government area of Ogbomoso, Oyo State during the 2015 growing season. Eight (8) control treatments were evaluated namely: Weed control with Atrazine, Diuron, 2 hoe weeding, 3 hoe weeding, Black plastic mulch, grass mulch, Diuron + Atrazine + Plastic mulch (IWM) and unweeded plot. The three (3) hoe weeding and the unweeded plot served as the control treatments. The experiment was laid out in a Randomized complete block design with three replicates. Yam setts were planted at a spacing of 1 m x 1 m to give a population of 10000 plants/ha. Atrazine and Diuron were applied at the rate of 2.5 kg a.i/ha, 2 hoe weeding was done at 3 and 6 weeks after planting (WAP), 3 hoe weeding was done at 3,6 and 9 WAP, while grass mulch was applied at the rate of 5 tons/ha. In IWM, Atrazine and Diuron were applied each at the half recommended rate (1.25 kg/ha) before applying plastic mulch. The treatments were applied pre-emergently on a rain wetted soil after planting. Data were collected on growth and yield parameters of yam as well as on Tithonia weed population and dry matter yield. Results showed that weed control methods significantly (P < 0.05) influenced water yam yield. The highest tuber yield (21 tons/ha) in plastic mulch was comparable to IWM (20 tons/ha), 3 hoe weeding (19 tons/ha) and 2 hoe weeding (18 tons/ha). Grass mulch (16 tons/ha), Diuron (15 tons/ha), Atrazine (14 tons/ha) were also not significantly (P > 0.05) different. Thus, it may be concluded that plastic much is the most efficient of the methods for weed control in yam. The implication of this finding is discussed.