Influence of grain types and graphene nanopowder characteristics on insecticidal efficacy against common grain...

The increasing resistance of insects to chemical-based pesticides is a critical challenge in crop production, demanding the urgent development of sustainable and effective pest control alternatives. In response, this study presents the insecticidal potential of graphene materials in the form of nanopowders as new chemical and resistance free grain protectants. The influence of the grain types such as rice, maize, and wheat and graphene nanopowder characteristics on insectidicial efficacy against common grain insects was evaluated against three most destructive grain insects including: the rice weevil, Sitophilus oryzae (L.) (Coleoptera; Curculionidae), the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera; Curculionidae), and the red flour beetle, Tribolium castaneum Herbst (Coleoptera; Tenebrionidae). Three industrially produced graphene nanopowders with distinct physicochemical properties (particle size, surface chemistry, hydrophobicity) were used at two dosage rates (500 and 1000 ppm). Mortality of insects was assessed after 7, 14, and 21 days of exposure, and progeny production was evaluated after 65 days. The results indicated that S. oryzae exhibited the highest susceptibility among the tested species, with rice grains experiencing the most significant insect mortality across all graphene concentrations (500 and 1000 ppm). Significant reductions in progeny with minor produced insects were observed, especially in maize, highlighting the long-term protective effects of graphene nanopowders. The insectidicial mode of action is attributed to a physical mechanism involving the adhesion of graphene particles to insect bodies, obstructing respiration and disrupting the cuticle. These findings suggest that graphene nanopowders, due to their unique structural, chemical and interfacial properties, have a strong potential to be used as new grain protectants, providing unique physical mode of action.