Development of a test design for a semi-field, colony feeding study for the common eastern bumble bee (Bombus impatiens [Hymenoptera:Apidae])

Ecological risk assessment is a key component of the regulatory process
required for registration of crop protection products around the world.
The western honey bee (Apis mellifera) is the model organism for pesticide
risk assessments for bees, but there are uncertainties over whether it is
predictive of risks to other bees. Consequently, efforts are underway to
develop test methodologies for other non-Apis bees. We conducted a
semi-field colony feeding study with Bombus impatiens colonies to develop
a colony-level methodology for bumble bees. We exposed commercially
available bumble bee colonies to diets consisting of four concentration
treatments of dimethoate insecticide (0.05, 0.19, 0.75, and 3.0 mg a.i./L)
via supplemental sugar solution for six weeks and compared exposed
colonies to untreated controls. Each treatment group had 10 replicate
colonies, with one replicate per treatment group represented at each of
the 10 study rural locations. We collected data on various colony-level
endpoints including production of female reproductive (gyne) offspring,
colony weight, foraging activity, and consumption of provisioned sugar
solution. Our results indicated that the test design could be used to
derive concentration-response relationships for several endpoints
including the most sensitive, colony mass (No Observed Adverse Effect
Concentration = 0.05 mg a.i./L). Overall, our study provides the
foundation for a semi-field, colony feeding study test design for bumble
bees, thus adding to the growing body of studies that may be used to
assess the protectiveness of the honey bee risk assessment framework for
non-Apis bees exposed to pesticides.