Pest status and ecology of bean stem maggot (Ophiomyia spp.: Diptera: Agromyzidae) on the Niassa Plateau,Mozambique

Research was carried out on the Niassa Plateau, northern Mozambique, with the aim of determining the phenology and importance of bean stem maggot (BSM) (Ophiomyia spp.: Diptera: Agromyzidae) on common beans. The objective of the study was to gather information in order to develop elements of an integrated control programme against BSM for use by farmers in the local cropping system, characterized by limited access to external inputs. Date of sowing trials were used in six consecutive rainy seasons to determine infestation rate of BSM during the main bean growing season and to determine damage due to the pest. These trials were also used to evaluate insecticide treatments against BSM and, at the same time, to undertake a survey of BSM parasitoids and the rates of parasitism from puparia collected at each sowing date. It was observed that infestation rates of BSM increased with delay in date of sowing in each of the two growing periods during the season and that percentage plant loss and yield decrease was correlated with number of BSM per plant. Insecticide seed treatmentwas effective in reducing infestation rates. BSM has two main parasitoids that probably play a role in limiting BSM population towards the end of the first growing period.