Low concentrations of selenium nanoparticles enhance the performance of a generalist parasitoid and its host, with no net effect on host suppression

Abstract

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) onAnisopteromalus calandrae(Howard) (Hymenoptera: Pteromalidae), a generalist parasitoid of stored product pests. RESULTS: The LC50 of SeNPs was 1540 mg L−1for female parasitoids and 1164 mg L−1for 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−1for females and by 35% at 13.83 mg L−1for 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 beetleCallosobruchus 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.