Assessing the diversity of insect pests in grain legumes using different light traps

A set of three types of light traps namely black light at rooftop, black light above ground, and normal light above ground were installed at five places of the open grain legumes cropping area of Grain Legumes Research Program, Khajura, Banke, Nepal from January to December, 2017 for evaluating comparative efficacy of light trap on monitoring the abundance, diversity and population trends of important insects with elevation and prevailing weather conditions. Black light trap was found more effective for monitoring vague diversity of insect species and their abundance than ordinary light trap. Placing black light trap at higher elevation further increased its efficiency to attract many species of night flying adult population (1419 adults comprising of 35 species) as compared to the same trap placed above ground level (766 adults with 35 species) and ordinary trap placed above ground level (701 adults with 33 species). Higher number of insect species (31) were captured in black light trap placed at higher elevation in spring night followed by clear night (22), rainy/cloudy night (10) and winter night (5), respectively. This indicates the abundance of insect population is higher in spring and reaching to few numbers in winter season. As the environment and cropping system is changing, continuous monitoring of insects is required to have their better estimates and information in advance for their management.