Pests and diseases in green manure legumes: Prevalence and management

Abstract

Pests and diseases are a major constraint to agricultural production in the tropical regions. several factors such as intensive cultivation, monoculture, tillage practices, use of agrochemicals, and decrease in soil fertility have increased pest and disease incidences. Short fallows involving green manure legumes are increasingly being researched as well as cultivated by farmers in Kenya. One of their benefits is the control of diseases and pests. Green manure legumes have numerous positive impacts on pest and disease incidence due to both biological and chemical effects and through increasing soil fertility leading to greater plant vigour. A greenhouse and field study activities were carried out under the Legume Research Network Project activities on the impact of several green manure legumes on the incidence of root knot nematodes Meloidogyne spp. The study identified some green manure legumes to have potential to reduce nematode populations in the soils. Crotalaria (juncea, ochroleuca), Mucuna pruriens (black and white) and Desmodium uncinatum were found to be poor hosts or non-hosts to these nematodes while Phaseolus coccineus (scarlet, white), Vigna unguiculata (M66, K80) were rated as intermediate hosts. Lablab purpureus (black, cv. Rongai), and P. coccineus (white) were rated as good hosts. There is evidence on shared pests and diseases among the green manures and main crops implying that before introducing a particular green manure in a location, one should determine the pest and disease host range status of the green manure legume. Attempts should be made to develop country and region-specific information databases through coordinated surveys and efficacy trials and use the existing networks to develop strategies that can quickly control these diseases. The incorporation of green manure legumes should therefore be viewed as a component of a comprehensive strategy for the control of pests and diseases which includes clean planting material and resistant crop genotypes.