Influence of intercrops on pests’ populations in upland rice (Oriza sativa L.)

We conducted a 3 x 4 factorial experiment fitted into a randomized complete block design, using three intercrops: cowpea (Vigna unguiculata L. Walp) at 0, 50,000, 100,000, 150,000 plants/ha; groundnut (Arachis hypogea L.) at 100,000, 200,000, 300,000 plants/ha; and egusi-melon (Colocynthis vulgaris L.) at 10,000, 20,000, and 30,000 plants/ha to evaluate their influence on incidence of stem borer (Chilo zacconius) (Blesz) and the green stink bug (Nezara viridula (L.)) in upland rice (Oryza sativa L.) .The experiment was conducted during the wet and dry seasons of 2004. Rice/cowpea recorded the highest incidence of N. viridula (3.1, 3.3%) compared to rice/groundnut (1.3, 1.3%) and rice/egusi, (1.8, 1.8%) during the wet and dry seasons respectively. Intercrop with groundnut significantly (p 0.05) reduced stem borer (C. zacconius) incidence to 7.4 and 13.2% respectively for wet and dry season cultivation compared with the control (12.0 and 18.0%). Rice and groundnut (100,000 - 200,000 plants/ha) intercrop is recommended for reduced incidence of C. zacconius and N. viridula. This result demonstrates that a careful selection of crop combination and plant population could lead to reduced insect pests’ incidence in upland rice.Key words: intercrops, plant populations, pest incidence, Oryza sativa, Chilo zacconius, Nezara viridul