Management of Tribolium castaneum using synergism between conventional fumigant and plant essential oils

Conventional fumigants, used to control stored grain insect pests, have not only led to environmental and health concerns, but also raised insecticide resistance development in insect pests. Their efficiency is diminishing owing to variable degree of application, accuracy, exposure time, conditions and frequency of usage. Red Flour Beetle (RFB), Tribolium castaneum, is pest of high economic importance in stored grain products. It was trialed for evaluation of entomotoxicity of plant essential oils (Calotropis procera, Azadirachta indica, Eucalyptus camaldulensis, Datura stramonium and Nicotiana tabacum) and phosphine gas at various concentrations alone and synergistically. Results depicted that essential oil of N. tabacum and phosphine gas caused the highest mortality (65% and 80%, respectively) at their highest concentrations (15% and 500 ppm). The highest synergistic toxic effect was observed for N. tabacum and A. indica essential oils at 500 ppm + 15% combination while the least synergistic toxic effect was observed in E. camaldulensis (37% mortality) with respect to the control treatment. Progeny development in the treated RFB females was significantly suppressed by the higher concentrations of plant essential oils and phosphine gas. Similarly, Phosphine combinations with N. tabacum and C. procera significantly suppressed the F1 progeny multifold as compared to control treatment. Eco-friendly biopesticides based on plant extracts or oils, with affirmative synergism, can be integrated as part of management module to control stored grain insect pests for a safer food storage and supply.