Influence of Maize and Soybean Intercropping Patterns on major Insect Pests and yield of Soybean (Glycine max (L) Merrill) in South Eastern Nigeria

Abstract

The influence of various soybean and maize intercropping patterns on major insect pests and yield of soybean were studied in the 1995 and 1996 planting seasons (July -September) at Umudike, south eastern Nigeria. The most prevalent insect pests found infesting soybean at the vegetative and early flowering stages, 2 weeks after planting (WAP) to 8 WAP in all the intercropping patterns were the defoliators, Monolepta duplicata Sahl. and Ootheca mutabilis Linnaeus. The stink bugs, Nezara viridula Linnaeus and Aspavia armigera Fabricuis attacked soybean plants from 8 WAP to 14 WAP, at the reproductive stage up to the pod drying stage. During both years, the peak populations for the defoliators and stink bugs ranged from 4 WAP to 5 WAP and 10 WAP to 11 WAP, respectively. Soybean planted sole had more leaf damage and significantly (P = 0.05) higher incidence of M duplicata, O. mutabilis, N. viridula and A. armigera than in other cropping patterns, with soybean planted on the crest of the ridge in the maize/ soybean intercrop being the least infested. Seed yields were significantly (p=0.05) higher when soybean was planted on the crest of the ridge in the maize/soybean intercrop than in other intercropping patterns. Seed yield reductions of 16.0% and 12.5% were obtained in the sole cropping compared with when soybean was planted on the. crest of the ridge in the intercrop, in 1995 and 1996, respectively. The study suggests that maize offered protection to soybean in the mixture by reducing the population of defoliators and stink bugs which resulted in reduced yield losses