Effect of temperature and relative humidity on the effectiveness of graphene on stored product insects.

This investigation assessed the insecticidal efficacy of two graphene formulations (Gr1 and Gr2) on wheat kernels against adults of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) in relation to temperature and relative humidity (RH) at concentrations of 500 and 1000 ppm. These bioassays were conducted in all possible combinations of three temperature levels: 20, 25, and 30 °C, as well as two relative humidity levels (55 and 75%). Progeny production was also evaluated 65 days later. The species that emerged as the most susceptible to graphene-treated wheat kernels was O. surinamensis compared to S. oryzae, regardless of temperature, RH, dose, and graphene formulation. At high RH levels, increasing temperature led to a decrease in mortality of S. oryzae in both Gr1 and Gr2, whereas at low RH levels, the results were dependent on the dosage of graphene formulation. At 75% RH, mortality ranged at significantly lower rates compared to their corresponding ones at 55% RH, while RH appeared to have no effect at 20 °C regardless of graphene formulation. Total inhibition of the emergence of progeny production was recorded for O. surinamensis, while graphene failed to suppress the progeny of S. oryzae. The current study's findings offer evidence supporting the feasibility of using graphene as an alternative to chemical-based pest control approach for protecting grain stored products.