EVIDENCE THAT HONEY BEE ASSOCIATIVE LEARNING IS IMPAIRED BY GLYPHOSATE TRACES

LUCILA T. HERBERT; ANDRÉS ARENAS; WALTER M. FARINA

Huerta Grande

Congreso; 2nd Latin American Meeting of Chemical Ecology - ALAEQ; 2012

Latin American Association of Chemical Ecology - ALAEQ

Glyphosate (GLY) is a broad spectrum herbicide used for weed control. During the evaluation stages for product approval, only lethal effects studies on invertebrates were reported. However, the possibility that GLY causes sub-lethal damage to non target organisms such as insects that forage in agricultural ecosystems cannot be discounted. Honeybees are the main agricultural pollinators and a well known model for learning and memory research. We studied the putative effects of GLY on the behavior of honeybees, specifically on their associative learning abilities through different integrative experiments: 1) Laboratory reared bees of 15 days of age and exposed to GLY at least during their first weed as adults, were trained to establish and elemental association through an olfactory conditioning of the proboscis extension response (PER), which consisted in three odor-reward association trials. 2) Bees captured at the hive entrance were trained to a longer elemental learning protocol (PER conditioning of eight odor-reward association trials and five extinction tests) in which the sucrose reward contained sub-lethal doses of GLY. 3) Bees were trained to a non-elemental learning paradigm (negative patterning) also with contaminated sucrose reward offered during PER conditioning. Mortality, solution uptake and locomotor activity (LA) were recorded for laboratory reared bees and acquisition curves and memory retention were recorded for all the tested subjects. Mortality, food uptake and LA did not differ between treated groups. Elemental and non-elemental associative learning was however, impaired by GLY traces. Memory retention at short term differed between treatments for experiment 2), but no differences were found at a longer time scale for the rest of the experiments. These results imply that GLY at concentrations found in nature as a result of standard spraying could impair associative learning between a floral odor and its nectar, which in turn would have negative consequences on honeybee foraging.