Low doses of selenium nanoparticles enhance the performance of the generalist parasitoid Anisopteromalus calandrae

BACKGROUND The environmental and economic costs of conventional insecticides have stirred an interest in alternative management tactics, including the use of nanotechnologies. Selenium nanoparticles (SeNPs) have many applications in agriculture but may not be compatible with biological control; however, low concentrations of SeNPs may benefit natural enemies via hormesis. This study investigates the dose-dependent effects of SeNPs (0–1000 mg L⁻¹) on Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), a generalist parasitoid of stored product pests.

RESULTS The LC₅₀ of SeNPs was 1540 mg L⁻¹ for female parasitoids and 1164 mg L⁻¹ for males (which was not significantly different between sexes). SeNPs had a significant hormetic effect; average lifespan increased by 10% at a dose of 4.03 mg L⁻¹ for females and by 35% at 13.83 mg L⁻¹ for males. In a bioassay including hosts, low-dose SeNPs (25 mg L⁻¹) enhanced female performance; lifespan increased by 23% and the number of offspring increased by 88%. However, the number of emerging hosts (azuki bean beetle Callosobruchus chinensis (L.) (Coleoptera: Chrysomelidae: Bruchinae)) did not significantly decrease; in the absence of parasitism, SeNPs improved emergence by 17%.

CONCLUSION Because higher concentrations of SeNPs reduced parasitoid lifespan, whereas low doses enhanced not only parasitoid performance but also host emergence, practitioners will need to pay special attention when optimizing SeNP formulations to maximize their contribution to pest control or in the mass rearing of insect parasitoids.