Honey bee behavioral responses to xenobiotics

Many studies have examined how bees respond to xenobiotics. However, most of these studies involved forcing bees to ingest xenobiotics in no-choice assays. Under natural conditions, food sources of honey bees are rarely limited to one choice. To characterize honey bee behavioral responses to potential xenobiotics at sublethal doses when alternate food is available, we tested discriminatory behavior in free-flight and small-cage choice assays. In this study, several natural xenobiotics and synthetic toxicants were tested. We found honey bees avoid quinine, a natural alkaloid, after only a brief exposure; this behavior was consistent in both free-flight and small-cage assays.. Foragers also prefer quercetin, a flavonoid which occurs frequently in nectar, when it is present in sugar syrup at concentrations of 0.1mM, and 0.25mM. For synthetic chemicals, atrazine, the most widely used herbicide in the US, and chlorothalonil, a common fungicide found as a contaminant in bee hives, were tested. In our small-cage preference assay, bees exhibited a preference for the 1ng/ml atrazine sucrose syrup group compared with control but no preference was detected for atrazine at other concentrations. However, free-flight choice assays showed that bees preferred atrazine in 0.01ng/ml and 0.1 ng/ml treatments over controls. For chlorothalonil, bees showed an avoidance response to relatively low concentrations (0.05ng/ml, and 5ng/ml) but a trend  toward a preference for chlorothalonil at relatively high concentration (50 ng/ml) in the first 24 hr period of the small-cage assay. No preference or avoidance of chlorothalonil was detected in free-flight tests. In our ongoing study, we will continue to assess bee behavioral responses to synthetic pesticides that are encountered by foragers in agricultural landscapes and by all bees in the hive environment.