Research on insecticidal efficacy of different inert dusts against the maize weevil (Sitophilus zeamais Motschulsky, Coleoptera, Curculionidae) adults

Abstract: In the search for an effective and sustainable control method against the maize weevil (Sitophilus zeamais Motschulsky), an important insect pest affecting stored grain, different inert dusts were tested under laboratory conditions. We treated wheat grains with quartz sand, zeolites, and diatomeaceous earth. Inert dusts of different origins were used, namely diatomaceous earth from Slovenia and SilicoSec, quartz sands from two locations from Slovenia, and three different zeolites (two types of natural zeolite from location in Slovenia, and synthetic zeolite Asorbio®). Untreated winter wheat grains served as control treatment. The substances were tested at three different temperatures (15, 20 and 25 °C) and two different relative humidity levels (55 and 75%). Mortality was measured 7th, 14th and 21st day after exposure. Inert dusts were applied at two different concentrations, 450 and 900 ppm. The analysis of pooled results provoked significantly the highest mortality of beetles in treatments with SilicoSec® (52.31 ± 2.07%), and in treatment with one type of Slovenian zeolite (31.48 ± 1.42%). The lowest mortality was recorded in treatments with quartz sands from both Slovenian locations, Moravče (18.84 ± 1.31%), and Raka (9.12 ± 0.66%). Mortality of S. zeamais was significantly the highest in treatments exposed to 25 °C (28.32 ± 1.16%), and in treatments exposed to higher concentrations (900 ppm) of inert dusts (27.30 ± 0.87%). The use of diatomaceous earth is well established in stored products pest management, however the knowledge on the efficacy of zeolites is very week and offers a lot of opportunities for future researchers.