Bioactivity of diatomaceous earth to Sitophilus zeamais (Coleoptera: Curculionidae) in different application conditions

The objective of this study was to evaluate the insecticidal activity of diatomaceous earth (DE) at different ambient temperatures on adult Sitophilus zeamais and progeny, using different doses and exposure periods. The experiments were performed in Petri dishes containing 40 g of the whole corn kernel, treated with DE at doses of 0, 0.25, 0.5 and 1.0 kg Mg-1. Each dish was infested with 25 S. zeamais adults and kept at climatic chambers under temperatures of 20, 25, 30, 35 and 40 oC. The insect mortality was recorded after six and 15 days from the beginning of the bioassays. The grains evaluated at 15 days were separated from insects and kept in the dishes for another 75 days under the same temperature conditions. After this period the effect of ambient temperature and of diatomaceous earth doses on the emergence of S. zeamais in the F1 generation was evaluated. It was found that the mortality of S. zeamais increased with the higher dose and temperature during the exposure period of six and 15 days. The number of insects emerged reduced with increasing temperature in these two exposure periods. The increase of temperature and exposure period favored the efficacy of DE in lower doses for control of S. zeamais.