Using a two-level system to test toxicity to honey bees (Apis mellifera) for development of pollinator-friendly pesticide adjuvants

Off-target pesticide drift from cropland is a major source of pesticide exposure to pollinating insects, including honey bees. Adjuvants are added to pesticides to improve effectiveness against crop pests but can be equally or more toxic than active ingredients. There is an urgent need to develop and use nontoxic adjuvants. In this study, we used a two-level system, a honey bee cell line (AmE-711) and whole bees, to test the toxicity of two newly identified plant-based adjuvants, sodium alginate (SA) and a fenugreek polymer (FP), along with a petroleum-derived industry-standard polyacrylamide (PAM). Results showed that SA and FP were markedly less toxic to AmE-711 cells than PAM. The data is consistent with results from caged honey bee toxicological studies, demonstrating the applicability of AmE-711 cells to pre-screen for non-toxic (or less toxic) pesticide tank mix products before using whole bees as assay subjects. In combination with laboratory testing of the drift reduction potentials of adjuvants and pesticide spray mix, this two-level system helps select suitable candidates to test in field studies, improving efficiency and reducing costs in the research and development process of pollinator-friendly adjuvants and pesticide applications.