Meeting Abstract
Global declines in honeybees (Apis mellifera) have been linked to Colony Collapse Disorder (CCD), a phenomenon that occurs when worker bees disappear from the colony, leaving the brood unattended. While there is no single cause of CCD, sublethal doses of pesticides cause physiological and behavioral changes that adversely affect hive health. This research aims to determine: 1. if motor functions of bees are impaired after treatment with sublethal doses of imidacloprid, and 2. if dose-response curves differ in bees collected in early summer vs. late summer. Honeybee foragers collected from apiaries in central PA were harnessed, fed to satiation, and after 22-24 hours, randomly assigned to control or various treatment groups. Control bees were fed 10 µl of 1.5 M sucrose. Bees in treatment groups were fed with imidacloprid (Macho®4.0, AgriStar) at doses of 1/5th,1/10th,1/20th, 1/50th,1/100th, or 1/500th of the LD50 (18 ng/bee). Four hours post-treatment, motor tests were conducted: abdomen and leg movement, antennae movement, and proboscis extension reflex. Scores of 0 (no function), 1 (impaired function), and 2 (full function) were assigned. A logistic regression model showed an effect of imidacloprid on motor responses. While the dose-response curves differed between bees collected in early summer vs. late summer, motor responses of bees were consistently impaired at 1.8 and 3.6 ng/bee in early and late summer bees. These results suggest that sublethal doses of imidacloprid in the range that bees are exposed to in the field impair motor function, a factor that may negatively affect hive health. Bees collected in early summer showed a greater frequency of impairment at higher doses of imidacloprid when exposure to local agrichemicals was likely to be high.
