Does a herbicide affect appetitive behavior in the honeybee Apis mellifera?

FARINA WALTER M.; HERBERT L; A. ARENAS

Guangzhou

Simposio; First International Symposium on Insecticide Toxicology; 2014

Glyphosate (GLY) is a broad spectrum herbicide used for weed control. During the evaluation stages for product approval, only lethal effect studies on invertebrates were reported. Sub-lethal damage of GLY to non-target organisms such as insect pollinators has not been evaluated until now. Honeybee Apis mellifera is the main pollinator in agricultural environments and a well-known model for behavioral research. Moreover, honeybees are also accurate biosensors to determine environmental pollutants and their appetitive behavioral response is a suitable tool to test sub-lethal effects of agrochemicals. With this in mind, we studied the effects of field-realistic doses of GLY on honeybees exposed chronically or acutely to this herbicide. We focused on sucrose sensitivity, olfactory conditioning of the proboscis extension response (PER) and foraging related behavior in honeybees. Results show that mortality, food uptake and locomotive activity did not differ between treated groups. However, reduced sensitivity to sucrose and learning performance were found for the groups chronically exposed to concentrations of 2.5 and 5.0 mg/L of GLY (values within the range of recommended doses). When olfactory PER conditioning was performed with sucrose reward that contained the same GLY concentrations (i.e. acute exposure), elemental associative learning and short-term memory retention decreased significantly for the treated group. Altogether, these results imply that GLY at concentrations found in agricultural settings as a result of standard spraying can reduce sensitivity to nectar reward and impair associative learning in honeybees. However, no effect on foraging and recruiting activity was found. Our results suggest that successful forager bees can become a source of a constant inflow of nectar with GLY traces into the hive, which in turn could have long-term negative consequences on colony survival.