Efficacy of recovered diatomaceous earth from brewery to control Sitophilus zeamais and Acanthoscelides obtectus

Diatomaceous earth (DE) is an inert dust that can be used as a filter in breweries and to control stored-product pests. Experiments were carried out with two DE types to identify their persistence in mini-silos, control of progeny, and mortality of Sitophilus zeamais and Acanthoscelides obtectus in maize and common bean grains. We used DEs from a brewing industry, a conventional DE (directly used as a filter for beer clarification) and a residue DE (a DE recovered after its use as a filter). Experiments were conducted considering the exposure time of insects to the DEs (1, 3, 5, and 7 days for A. obtectus and 5, 7, 10, and 18 days for S. zeamais), concentration (0.5, 1.0, 1.5 and 2.0 g/kg) and persistence (evaluations performed every 30 days). Mortality of both insects increased with concentration (96 and 59% for A. obtectus at the most efficient concentration and 80 and 9% for S. zeamais at 2.0 g/kg for conventional and residue DE respectively) and exposure time (100 and 90% for A. obtectus and 98 and 51% for S. zeamais at the highest exposure time for conventional and residue DE respectively). We observed a decrease of insects in the progeny (>80% at the highest concentration or period of exposure). Persistence control was high for A. obtectus in both DEs (>95% control after 70 days of exposure) while for S. zeamais conventional DE was better at maintaining low insect populations (87 and 50% for conventional and residue DE respectively on the 50th day of exposure). The use of DEs from the brewery industry can be considered as an alternative tool to control populations of stored-product pests.