Insecticidal Effects of Native Raw and Commercial Diatomaceous Earths Against Lesser Grain Borer and Granary Weevil Under Different Environmental Conditions

Stored grain pests cause significant economic losses during cereal grain storage. Insecticides have long been central to pest control, but growing concerns over resistance, environmental harm, and human health demand alternative strategies. Diatomaceous earths (DEs) are safe, eco-friendly alternatives, though their efficacy depends on factors like temperature, humidity, dose, and insect species. This study assessed the insecticidal effects of two native raw (Ankara and Aydin) and one commercial (Silico-Sec) DEs against Rhyzopertha dominica (F.) and Sitophilus granarius (L.) on stored wheat. Five DE doses (0, 250, 500, 750, 1000 ppm) were tested under two temperatures (25°C, 30°C) and two humidity levels (40%, 60%). Mortality was assessed at 7, 14, and 21 days after treatment (DAT). All DEs caused higher mortality in S. granarius than R. dominica. The highest mortality occurred in S. granarius at 30°C and 40% RH with the highest dose. Aydin DE was most effective, but did not reach 100% mortality in S. granarius by 21 DAT. In contrast, it caused complete mortality in R. dominica under the same conditions. Survivors of both species produced no F1 progeny. Given similar conditions in Turkish storage facilities, native Aydin DE is a promising control option.