Insecticidal Effect of Diatomaceous Earth Formulations for the Control of a Wide Range of Stored-Product Beetle Species

Simple Summary Inert dusts are promising alternatives to conventional insecticides against numerous stored-product insect species. Diatomaceous earth formulations are based on natural substances and are registered for direct application on grain in many parts of the world. The objective of this study was to evaluate the effectiveness of three diatomaceous earth formulations (namely Silicid, Celatom(& REG;) MN-23, and SilicoSec(& REG;)) against adults of a wide range of stored-product beetle species. Specifically, seven stored-grain beetle species were tested, including three primary colonizers and four secondary colonizers, which are commonly found in stored cereals and other relevant commodities in Greece. The experimental units for the bioassays were plastic cylindrical vials. Twenty grams of soft wheat was filled in each vial and twenty adults of each species were placed in each vial, with a separate series of vials for each species. Mortality levels were recorded after 3, 7, 14, and 21 days of exposure. After that, the vials were kept for additional 65 days to assess progeny production. Our results indicate that among the tested diatomaceous earth formulations, the application of Silicid resulted in complete control of the major stored-product insect species. Offspring production was noted only for primary colonizers. Diatomaceous earth (DE) formulations are promising alternatives over the use of traditional insecticides. In the present study, a series of laboratory bioassays was carried out to assess the efficacy of three diatomaceous earth formulations, i.e., Silicid, Celatom(& REG;) MN-23, and SilicoSec(& REG;), for the control of a wide range of stored-product insect species in soft wheat. The species tested were Tribolium confusum, Tribolium castaneum, Sitophilus oryzae, Sitophilus granarius, Rhyzopertha dominica, Oryzaephilus surinamensis, and Alphitobious diaperinus. Different dose rates, i.e., 0 (control), 100, 300, 500, and 1000 ppm, were used for each of the aforementioned dust formulations. Mortality levels of the exposed individuals were assessed after 3, 7, 14, and 21 days of exposure. Moreover, progeny were counted 65 days later. Based on our results, dust formulations were effective for the control of most of the stored-product beetle species tested. Among the DE formulations tested, Silicid could adequately control the stored-product insect species. Complete suppression of offspring was observed only for secondary species (T. confusum, T. castaneum, O. surinamensis, and A. diaperinus). For primary species (S. oryzae, S. granarius, and R. dominica), the lowest number of progeny was observed in wheat treated with Silicid. For instance, in the case of R. dominica, significantly fewer individuals were produced in Silicid-treated wheat at the highest dose rate. The results of the present study aim to encourage the utilization of DE in stored-product protection as an integrated pest management tool. Additional experimentation is required to apply the tested DE formulations in the field and on different surfaces.