The utility of bumble bee (Bombus impatiens) microcolonies for evaluating the effects of pesticides on brood

Many agricultural crops rely on pollination services provided by a large number of bee species. The honey bee (Apis mellifera L.) is used as a surrogate species for pollinator risk assessment, however there is uncertainty that a honey bee risk assessment may not be protective of other bee species due to different sizes and life histories. Bumble bees (Bombus sp.) are one of the most prominent pollinator species on the landscape and commonly utilized in commercial pollination services. Bumble bees differ from honey bees in their degree of sociality, morphology, and life history, making them a strategic alternative surrogate for pollinator risk assessments. Here we describe recent developments of a test method for bumble bees to assess the chronic toxicity of a compound to immature bumble bees. The initial test set-up is composed of five newly-eclosed female workers, pollen, and a 50% sucrose solution. Dimethoate and diflubenzuron, two common toxic reference compounds for laboratory bee testing, were orally fed to bumble bees through both pollen and sucrose routes of exposure. Analytical verification of the test diets has provided justification for our methods used to integrate a test substance into the diet. We will present how the microcolony study design fits within a pollinator risk assessment and what route of exposure is most appropriate for use when examining the effects of a compound on brood within the microcolony study design.