Management of Trogoderma granarium with insecticides alone is difficult due to its high tolerance to commonly used insecticides. In the present study, three organophosphorus insecticides (OPs), chlorpyrifos-methyl (CH), pirimiphos-methyl (PI) and malathion (MA) were evaluated alone or in binary blends with diatomaceous earth (DE), kaolin (KA) and zeolite (ZE) against T. granarium on stored wheat. The following concentrations were used: CH (2.5 and 5 ppm), PI (5 and 10 ppm), MA (4 and 8 ppm) and inert dusts (IDs) (500 and 1000 ppm). The number of dead larvae was counted 1, 2 and 3 weeks after exposure. Progeny (F1 and F2) was recorded 30 and 80 days after exposure, respectively. The wheat grain damage was measured at the end of experiments (80 days). The results revealed that the mortality of khapra beetle larvae was higher in all binary mixture treatments of OPs and IDs than individual ones. The mixtures of CH with IDs caused complete larval mortality at application rate (5 ppm). The binary mixtures of PI or MA with IDs induced strong mortality of T. granarium larvae (>82%). Furthermore, the results indicate that the combination of CH and inert dusts or PI with ZE at the highest rate completely suppressed F1 and F2 progeny after 80 days of treatment. The lowest number of F1 and F2 progeny was recorded in wheat treated with MA (8.0 ppm) + DE (1000 ppm) with 1.0 and 1.6 adults/50g, respectively. The mixtures of OPs and IDs at the highest tested rate protected wheat grains against damage caused by insect for 80 days. The findings of the present study indicate that the binary mixtures of OPs, especially CH and IDs are highly effective for the control of khapra beetle and could be implemented in the management of this destructive invasive insect.
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