Bees under surveillance: using video-tracking to monitor honey bee activity after sublethal exposure to pesticides

Despite growing awareness of the potential consequences of sublethal effects of pesticides on bees, current EPA safety regulations for pesticides only require lethal toxicity testing for effects on bees. Sublethal effects, however, can be difficult to quantify. For this study, a video tracking software system, EthoVision® XT, was employed to monitor the activity of honey bees that were exposed to sublethal doses of tau-fluvalinate and imidacloprid. Tau-fluvalinate is used in the hive for control of Varroa mites while imidacloprid is a systemic neonicotinoid commonly cited as affecting bees after sublethal exposure. Honey bees were treated topically with tau-fluvalinate diluted in acetone at 0, 0.3, 1.5, and 3µg/ml doses. The imidacloprid was administered orally in a sugar-agar food containing 0, 0.005, 0.05, and 0.5ng/ml imidacloprid. EthoVision® XT measured differences between treatments over 24 hours in the distance that bees moved and the amount of time spent interacting and feeding. Bees treated with the higher concentrations of imidacloprid spent less time interacting and more time feeding while the lowest concentration appears to have had a stimulatory effect. Similarly, bees treated with higher doses of tau-fluvalinate interacted less than control bees and those treated with the low dose. These results suggest that these pesticides do influence bee activity at levels below the lethal dose or concentration currently used to assess product safety to bees. This study also validates the use of video tracking systems to monitor and quantify the activity of non-target insects exposed to pesticides at sublethal levels.