Entomopathogenic fungi raise the effectiveness of organophosphorus insecticides against Trogoderma granarium

Abstract

Treatment of wheat grains with three organophosphorus insecticides (OPs), chlorpyrifos-methyl (CH), malathion (MA) and pirimiphos-methyl (PI) alone and in combination with three entomopathogenic fungi (EPF) (Trichoderma harzianum (TH), T. citrinoviride (TC), and Metarhizium anisopliae (MA)) was carried in the current study to examine their control potential of Trogoderma granarium Everts. The application rates of OPs were: CH (2.5 and 5.0 ppm), MA (4.0 and 8.0 ppm) and PI: (5.0 and 10.0 ppm). The three EPF were tested at 1.0 × 10⁵, 1.0 × 10⁷ and 1.0 × 10⁹ spores/kg. The impact of treatments on mortality of larvae after 7 and 14 days, F₁ progeny after 30 days, F₂ progeny, and grain weight loss after 80 days was examined. Generally, the binary mixtures of OPs and EPF were significantly more effective in the controlling T. granarium larvae than OPs alone or EPF alone after 7 and 14 days of exposure. Also, the mixtures of OPs (CH, MA and PI) and EPF achieved full mortality (100%) 14 days post-exposure and at the highest tested concentrations. Furthermore, mixtures of OPs and EPF significantly reduced the progeny production of khapra beetle and full progeny suppression was resulted in almost combined mixtures of OPs particularly (CH or PI) and EPF. Likewise, all mixtures of OPs and EPF induced a full protection of grains (wheat weight loss = 0.0 %) 80 days post treatment. Our findings indicate that the combinations of OPs and EPF could be a suitable protective tool of stored commodities against T. granarium.