Incidence of Mesoplatys ochroptera Stål (Coleoptera: Chrysomelidae) on Sesbania sesban in pure and mixed species fallows in eastern Zambia G. Sileshi and P.L. Mafongoya* Zambia/ICRAF Agroforestry Project, P.O. Box 510089, Chipata, Zambia; *Author for correspondence (e-mail: mfongoya@zamnet.zm) Received 22 October 2001; accepted in revised form 1 July 2002 Key words: Gliricidia sepium, Integrated pest management, Mucuna pruriens, Macrotyloma axillare, Macropti- lium atropurpureum Abstract The sesbania beetle, Mesoplatys ochroptera Stål (Chrysomelidae: Coleoptera), is a serious defoliator of Sesbania sesban in eastern and southern Africa. Developing integrated pest management practices against the beetle is an important aspect of the adoption of S. sesban as an improved fallow species. Field studies were conducted in eastern Zambia with the objective of determining the incidence of M. ochroptera on S. sesban in pure and mixed species fallows. M. ochroptera did not successfully feed or breed on species other than S. sesban either in the pure or mixed species fallows. The density of adult and immature stages of M. ochroptera was higher in mix- tures of S. sesban with Mucuna pruriens, Macrotyloma axillare, Macroptilium atropurpureum or Crotalaria gra- hamiana compared to a pure S. sesban fallow. Although mixed fallows of S. sesban with M. axillare and M. pruriens may produce fodder, increase the amount and quality of organic inputs and improve nutrient cycling in the soil, they appear to be incompatible with management of M. ochroptera. Mixing S. sesban with G. sepium neither increased larval and adult populations of M. ochroptera feeding on S. sesban nor damage to it. While this mixture appeared to favour development of pupae to the adult stage, it increased mortality of emerging adults. Therefore, it is concluded that mixing S. sesban with G. sepium is more robust in nutrient cycling, improving resource utilisation and management of M. ochroptera on S. sesban. Introduction Improved fallows involving nitrogen-fixing legumes have been shown to replenish soil fertility and in- crease maize yield (Mafongoya and Dzowela 1999; Kwesiga et al. 1999). Sesbania sesban (L.) Merrill has been the main focus for the improved fallow tech- nology in eastern and southern Africa (Kwesiga et al. 1999). Other species including Sesbania macrantha Phil. & Hutch., Cajanus cajan (L.) Millsp, Tephrosia vogelii Hook f., Acacia anguistissima (Mill) Kuntze, Gliricidia sepium (Jacq.) Walp., Leucaena leucoceph- ala (Lam.) de Wit and Leucaena diversifolia (Schtdl.) Benth are also being tested for improvement of fer- tility in nitrogen-deficient soils in southern Africa (Kwesiga et al. 1999; Mafongoya and Dzowela 1999). More recently there has been an interest in mixed species fallows, as these are believed to increase the biodiversity and sustainability of the fallow system. The advantages of mixed species fallows include in- surance against failure, production of multiple prod- ucts, improved utilisation of available plant growth resources and reduction of pest pressure. In western Kenya, S. sesban + Crotalaria grahamiana Wight & Arn. and S. sesban + T. vogelii fallows were recom- mended for recycling of deep soil nitrogen, high in- puts from biological nitrogen fixation and fuel wood production. S. sesban + Macroptilium atropurpureum (DC) Urb. mixtures were also recommended for max- imising fallow biomass and fodder production (Gath- umbi 2000). Mesoplatys ochroptera Stål (Chrysomelidae: Co- leoptera) has become a serious defoliator of S. sesban 225 Agroforestry Systems 56: 225–231, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.