Effect of temperature on insecticidal efficiency of local diatomaceous earth against stored-grain insects

A study was conducted in 2017 in Entomology Laboratory of Kahramanmaras Sutcu Imam University to determine effect of temperature on insecticidal efficacy of local diatomaceous earth (DE), collected from Turkey, against the rice weevil, Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae), the confused flour beetle, Tribolium confusum du Val., 1863 (Coleoptera: Tenebrionidae), and the lesser grain borer, Rhyzopertha dominica (F., 1792) (Coleoptera: Bostrichidae). Bioassays were performed at three temperatures (20, 25 and 30 degrees C) and 55% RH on wheat treated with 0, 100, 300, 500, 900 and 1500 ppm (mg DE/kg grain) concentrations of local DE. Temperature had significant effect on insecticidal efficacy of local DE against the tested stored-grain insects. The effect of temperature on the insecticidal efficacy of local DE varied with insect species and concentration. Mortality of S. oryzae and T. confusum adults generally increased with increasing temperature and mortality at 30 degrees C was significantly higher than at 20 and 25 degrees C. However, for R. dominica adults treated with local DE, mortality at 20 degrees C was significantly higher than at 25 and 30 degrees C. The results indicated that complete mortality of T. confusum and S. oryzae can be achieved at lower concentrations ranging from 500 to 900 ppm. In conclusion, local DE formulation (ACN-1) has potential to be used for control of stored-grain insects.