Aging effect of two decade old technologies of bean stem maggot (Ophiomyia spp.) management options in Ethiopia: Baseline information generation for future research direction

Haricot beans are the most important food and cash crop for most of the Ethiopian farmers. However, bean stem maggot (BSM) (Ophiomyia species) is limiting the production of the crop particularly in dry areas. Three species are involved in the infestation: Ophiomyia phaseoli, Ophiomyia spencerlla and Ophiomyia centrosematis. Two decades ago, two management options of BSM were developed and used for the last twenty years. However, there is a tendency of decline in effectiveness. Hence, the current experiment was conducted to see the age effect  on the efficacy of BSM resistant varieties (Beshbesh and Melkae) and  high bean plant population density (400,000 plants ha-1) (narrow spacing). The experiments were conducted at Shalla (southern Ethiopia) and Omonada (Jimma). Randomized Complete Block Design (RCBD) in three replications was used as the experimental design. The plot size was 10 m × 10 m. The experiment was conducted in 2014 and 2015. The treatments were BSM resistant varieties (Beshbesh and Melkae), high bean plant population, standard check (Awash-1) and Imdalem (seed dressing chemical). For plant population treatment and Imdalem 70% WS seed treatment a bean variety Awash-1 was used as a planting material. Data collected include stand count, seedling percent mortality by BSM, vigorously score, number of larva per plant and grain yield. The data were analyzed using SAS software and mean separation was done by Tukey Standardized Range Test (p<0.05). In all parameters measured, Melkae bean variety become susceptible to BSM and cannot be used any more as a resistant variety. From the result of the experiment, it can be concluded that Beshebeshe bean variety, high plant population and Imdalem seed dressing can be used as integrated management of BSM in Ethiopia in general and study sites in particular.   Key words: Bean stem maggot, Imdalem 70% WS (Imdachloprid), seed dressing, plant population, resistant variety, two decades, proven technology.