Control of Sitophilus granarius and Sitophilus oryzae on stored wheat using low-rate combinations of natural zeolite with three insecticides

Abstract

The insecticidal potential of three insecticides (chlorpyrifos-methyl (CH), deltamethrin (DE), spinosad (SP)), zeolite (ZE) and their low-rate combinations was tested against Sitophilus granarius (L.) and Sitophilus oryzae (L.) adults. The application rates were: CH at 0.1, 0.5 and 1.0 mg/kg, DE at 0.2, 0.5, 1.0 and 2.0 mg/kg, SP at 0.1, 0.25, 0.5 and 1.0 mg/kg, and ZE at 100 and 500 mg/kg. Individual treatments with CH, DE or SP at 1.0 mg/kg induced 100, 83.9 and 76.2% mortality of S. granarius, and 95.5, 69.3 and 88.2% mortality of S. oryzae after 21 days, respectively. Treatment with ZE alone at 500 mg/kg caused 43.5 and 50.3% mortality of S. granarius and S. oryzae, respectively, after 21 days. The combined treatments of insecticides and ZE showed higher adult mortality than treatments with each insecticide or ZE alone. Combined treatments of CH (0.5 mg/kg) + ZE (100 mg/kg), CH (0.1 mg/kg) + ZE (500 mg/kg), CH (0.5 mg/kg) + ZE (500 mg/kg) and SP (1.0 mg/kg) + ZE (500 mg/kg) induced 100% adult mortality of both insects after 21 days. In addition, a mixture of DE (1.0 mg/kg) + ZE (500 mg/kg) caused 100% mortality of S. oryzae after 21 days. Progeny of both insects decreased significantly in all treatments compared by untreated wheat grain. The mixtures, CH (0.5 mg/kg) + ZE (500 mg/kg), DE (1.0 mg/kg) + ZE (500 mg/kg, SP (1.0 mg/kg) + ZE (100 mg/kg) and SP (1.0 mg/kg) + ZE (500 mg/kg), induced remarkable progeny reduction (≈100%) and complete protection of wheat grain (weight loss = 0.0%) against damage caused by insects for 90 days. Our results indicate that the combination of insecticides with ZE at low rates is a promising approach for the control of S. granarius and S. oryzae on stored wheat.