Insecticidal Potential of Native Diatomaceous Earth Against Sitophilus granarius (Coleoptera: Curculionidae)

The granary weevil, Sitophilus granarius is one of the serious pests of cereal crops worldwide. To control this pest, diatomaceous earth (DE) formulation consisted of diatoms, obtained from Niğde Province, Turkey, was tested against adults of the granary weevil, Sitophilus granarius (L.) under laboratory conditions (25±1°C, 60±5% RH). Diatomaceous earth was applied to wheat grain at the rates of 100, 250, 300, 500, 750, 1000, 1500 and 2000 mg/Kg. Adult mortalities were assessed after 7, 14 and 21 days. Mortality rates rose with increases in dosage and length of exposure. Significantly higher mortality (89.75±3.66%) after one week occurred in grains treated with the highest concentration (2000 mg/Kg). At the highest concentration (2000 mg/Kg), the mortality reached as high as 100% after 2 weeks, while the lowest significant percent mortality (1.00±1.00%) was recorded in the control one week after exposure and only increased to 3.53±0.00% after 3 weeks. Percent weight loss in grain was also determined after 21 days. A significantly higher percent weight loss (7.29±0.11%) was found in the control, while no weight loss was observed in grains treated with the highest concentration (2000 mg/Kg). The grains were also observed for adult emergence for a period of 45 days. More than 90% reduction in adult emergence was recorded at concentrations of 1500 and 2000 mg/Kg. Conversely, the highest number of adults emerged at a dosage of 100 mg/Kg and in the control, i.e. 114.67±7.42 and 143.33±11.66 adults, respectively. The present study proposed that DE might potentially be effective in controlling S. granarius based on its ability to cause desiccation to the insects’ protective cuticular wax layer. In order to develop environmentally sound control programs for in sito management of granary weevils, it will be necessary to expand the present study based on life table to get a comprehensive understanding and to determine the effect DE has on granary weevils and other grain pests when it is combined with plant extracts.