The root-knot nematode problem in sesbania fallows and scope for managing it in western Kenya

Abstract

Sesbania (Sesbania sesban), which is promoted as a short-duration-fallow species in eastern and southern Africa, is an alternative host to root-knot nematode (Meloidogyne spp.). Therefore, it is important to know the extent of sesbania infection by the nematode on farms and its effects to crops grown in rotation with sesbania. A survey of 14 farms in western Kenya indicated that sesbania was infected by root-knot nematode in all the farms. The potential to build up the nematode population was much greater on farms where maize (Zea mays) was previously intercropped with a susceptible bean (Phaseolus vulgaris). Screening of 30 single plant accessions of four sesbania provenances (Kakamega, Siaya, Kisumu, and Kisii) from western Kenya in pots indicated limited scope for selecting material resistant to the nematode. All four provenances were infested by the nematode, and they increased its population in soil and root. A rangewide collection of sesbania germplasm needs to be screened to determine the scope of finding nematode-resistant material. Transplanted seedlings produced in heat-sterilized, nematode-free soil showed less nematode infection than direct-seeded plants. However, both direct seeding and transplanting seemed to increase nematode population similarly. A number of Crotalaria spp. that were found resistant to nematodes can be considered as alternatives to sesbania-planted fallows, but further field-scale testing is necessary to select appropriate species based on biomass production. Among other species suitable for short-duration fallows, only pigeonpea (Cajanus cajan) and senna (Senna siamea) showed promise. Species such as neem (Azadirachta indica), casuarina (Casuarina junghuhniana), and grevillea (Grevillea robusta) that are suitable for boundary plantings were free from the root-knot nematode.