Innovative approaches to evaluating the effects of insecticides on non-Apis bees
Although no single cause has been identified, declines in some bee populations have been attributed to several environmental stressors including pesticides. Due to differences in life history and pesticide sensitivity, there is an ongoing international effort to develop toxicity testing methods that extend beyond honey bees (Apis mellifera) to include non-Apis bees. This presentation will discuss innovative research approaches and findings from laboratory studies performed using bumble bees (Bombus impatiens) and mason bees (Osmia lignaria). To evaluate the effects of chronic oral exposure to the insect growth regulator (IGR) diflubenzuron (0.1, 1, 10, 100 and 1000 µg/liter) on B. impatiens worker health and brood development, we used 6-week queenless microcolonies. Syrup and pollen consumption were significantly reduced for all diflubenzuron concentrations tested. Pupal cell production was decreased in the high-dose group. Drone production, a proxy for reproductive success, was inhibited in a concentration-dependent manner. To assess the toxicity of pesticides to O. lignaria, we developed and employed a novel modified spray tower design. Male and female O. lignaria adults were exposed by whole-body contact to premixed insecticide mixtures (each with a different mode of action). Mortality was monitored at 24, 48, 72 and 96-hours post treatment. Neonicotinoid and pyrethroid insecticides induced rapid mortality, while diamide (chlorantraniliprole), molting hormone agonist (methoxyfenozide) and IGR (spinetoram) chemistries induced gradual mortality. High mortality was recorded for all insecticide treatments (LD50<1 µg/bee) at 96-hours after application to adult mason bees at 96-hours post treatment. These studies provide insights into the effects of pesticides on under-studied species of non-Apis bees and provide a platform for continued methods development. Standardized methods are needed to support risk assessment activities and ultimately pollinator protection goals. This abstract does not represent U.S. EPA policy.