Efficacy of Azamethiphos for Grain and Surface Treatment Against Three Major Stored-Product Beetle Species

The present study evaluated the insecticidal efficacy of a commercial formulation containing azamethiphos (Teenox® EC) against adults of the saw-toothed grain beetle, Oryzaephilus surinamensis, the lesser grain borer, Rhyzopertha dominica (F.), and the granary weevil, Sitophilus granarius (L.), under laboratory conditions. The azamethiphos formulation was assessed both as grain treatment on wheat and barley at 0, 2.5, 5, 10 and 20 ppm for all species, and as surface treatment on concrete and plastic surfaces at 0, 0.125, 0.25, 0.5 and 1 μg a.i./cm2 for O. surinamensis and R. dominica. In grain treatments, adult mortality increased significantly with concentration and exposure interval for all species. Mortality was generally higher in barley than in wheat, particularly after longer exposure periods. Sitophilus granarius was the most susceptible species, reaching high mortality at the highest concentration, whereas R. dominica exhibited lower mortality responses, especially at lower concentration. Progeny production was significantly reduced with increasing concentration for all species, although the effect was more pronounced in barley than in wheat, particularly for O. surinamensis. In surface treatments, mortality was strongly influenced by surface type, with significantly higher efficacy on concrete compared to plastic. Mortality increased with both concentrations and exposure time for all species, while interspecific differences were less pronounced than in grain treatments. These responses indicate that both substrate characteristics and exposure time are important parameters of azamethiphos efficacy. Overall, the results indicate that the azamethiphos formulation tested can provide effective control of key stored-product beetle species when applied either on grains or different surfaces, although its performance is influenced by commodity and surface type. These findings highlight the potential of azamethiphos as a versatile tool in integrated stored-product pest management programs.