Effects of Pesticides and Electromagnetic Fields on Honeybees: A Field Study Using Biomarkers

Abstract

The effects of pesticide mixtures and electric and magnetic fields on honeybees were evaluated in three experimental sites located in northern Italy: a control site far from anthropogenic-stress sources, a semi-natural site close to a high-voltage electric line and an agricultural site with intensive pesticide use. From each experimental site, young workers and foraging bees were taken monthly from May to October and analyzed for four enzymatic biomarkers: acetylcholinesterase (AChE), catalase (CAT), glutathione S-transferase (GST) and alkaline phosphatase (ALP). The results revealed time- and site-specific effects in respect to control site, confirming the role of biomarkers as diagnostic and early-warning tools for multi-stress sources on honeybees. In the electromagnetic-stress site, the effect of an over-activation of all analyzed biomarkers was observed at the end of the season. According to other literature findings, this event was related to a behavioral over-activation in a period in which bees should prepare themselves for overwintering. This finding poses potential problems for winter survival. In the pesticide-stress site, different pesticide-induced responses were identified. We demonstrated in the field that pesticide mixtures currently used in agriculture could greatly affect the biochemical parameters of bees (with both enzymatic under- and over-activations).