In-vitro evaluation of copper nanoparticles as a potential control agent against the fungal symbionts of the invasive ambrosia beetle Euwallacea fornicatus

Abstract

The tea shot-hole borer (THSB), a member of the Euwallacea fornicatus (Eichhoff 1868) complex of species, harboring the plant pathogenic symbiotic fungi (AF-6, AF-8, and Fusarium sp.) (Curculionidae: Scolytinae) attacks avocado (Persea americana Miller) and other tree species in Florida. Currently, their management is limited to prevention and sanitation; therefore, the development of novel control alternatives is critical to mitigate pest outbreaks and avoid massive crop losses. Here, we report on the antifungal activity of copper nanoparticles (Cu-NPs) against the beetle/fungus complex and their effect on the beetle's reproduction. The results revealed that the synthesized Cu-NPs were pure metallic Cu with an average size of 240.88 ± 62.66 nm measured by electron microscopy. The antifungal test for symbionts showed that 0.75 mg/mL of Cu-NPs caused growth inhibition above 60%. However, strong alterations in the morphology of fungal cells were observed at Cu-NPs concentrations as low as 0.1 mg/mL. Additionally, treatments with 0.25, 0.5, and 1 mg/mL of Cu-NPs led to a reduction in offspring production in a concentration dependent manner. According to our findings, the application of Cu-NPs could be potentially considered as an alternative for the control of the beetle-fungi complex or even be integrated into novel disease management strategies.