The genus Sesbania (Leguminosae) consists of many species used widely in the tropics for their nitrogen-fixing properties to improve crop production. Most of the perennial species provide animal fodder, fuel wood, fibres, paper pulp and commercial gum, while some (e.g. Sesbania exaltata (Raf.) Cory and Sesbania punicea (Cav.) Benth.) are known to be noxious weeds (Vogt & Cordo 1976; Evans & Rotar 1987).
Tag: insect pests
Insect pests and beneficial arthropod populations under different hedgerow intercropping systems in semiarid Kenya
Exploiting the principles of biological control of crop pests is an important management strategy for the resource-poor smallholder farmers of the tropics. The effects of nine hedgerow species on the abundance of major insect pests of beans and maize, and predatory/parasitic-arthropods were monitored over two cropping seasons and the intervening dry period. The tree/shrub species evaluated were Gliricidia sepium, Grevillea robusta, Senna siamea, Senna spectabilis, Flemingea congesta, Croton megalocarpus, Morus alba, Calliandra calothyrsus and Lantana camara. Arthropod abundance was monitored through counts of infested plants and using yellow pan and pitfall traps. Beanfly (Ophiomyia spp.) infestation was significantly higher in the presence of hedgerows (35%) than in their absence (25%). Hedgerows did not influence aphid (Aphis fabae) infestation of beans. In contrast, maize associated with hedgerows experienced significantly lower stalk borer (Busseola fusca and Chilo spp.) and aphid (Rhophalosiphum maidis) infestations than pure maize, the margin of difference being 13% and 11% respectively for the two pests. Ladybird beetles closely followed their prey, aphids, with significantly higher catches in sole cropped-plots than in hedgerow-plots and away from hedgerows. Activity of wasps was significantly greater close to hedgerows than away from them. Spider catches during maize season were 77% greater in the presence of hedgerows than in their absence, but catches during other seasons were similar between the two cropping systems. Differences among hedgerow species were not significant for most of the arthropods monitored, except that beanfly infestation was greater with Gliricidia hedgerows. The study indicates that the effect of hedgerows on pest infestations of crops and their role as refugia for predators cannot be generalized but depends on the specific arthropods.
Performance of sesbania sesban infested by the defoliating beetle mesoplatys ochroptera in Zambia
Developing integrated pest management practices against the defoliating beetle Mesoplatys ochroptera is an important aspect of the adoption of Sesbania sesban as an improved fallow species in southern Africa. The effect of defoliation by M.ochroptera on the growth of S. sesban(provenance Kakamega) was studied during 1998–2000 at Msekera Research Station in eastern Zambia. To determine the relationship between M. ochroptera densities and degree of defoliation, potted seedlings were infested manually with different densities of larvae and adults. Infestation of two to three month old seedlings with 5–30 larvae or adults resulted in less than 20% defoliation. Infestation of seedlings with 90–150 larvae(>3 masses of eggs) led to 80–100% and 50–80% defoliation in two and three months old seedlings, respectively. The time of infestation and degree of defoliation that lead to reduction in growth and biomass were determined using simulated (manual) defoliation of one to three months old S. sesban seedlings. Manual removal of 50–100% of the foliage atone and two months after transplanting (MAP) appeared to reduce plant height, basal diameter, primary branches, leaf and wood biomass compared to that done atthree MAP. Removal of 25–50% of the sesbania foliage three months after transplanting apparently leads to overcompensation. In sesbania, compensatory growth occurred when 25–50% of the leaves were defoliated three months after transplanting. Therefore, farmers need to protect sesbania seedlings from defoliation against insects such as M. ochroptera only during the first two months after transplanting.