Study type: Medical/biological study (experimental study)

Combined Effects of Pesticides and Electromagnetic-Fields on Honeybees: Multi-Stress Exposure. med./bio.

Published in: Insects 2021; 12 (8): 716

Aim of study (acc. to author)

The aim of the study was to investigate the combined effects of two possible stress sources for bees, pesticides and electric and magnetic fields by a field trial.

Background/further details

Multi-stress exposures are considered the most putative cause of honey bee decline.
Three experimental sites were chosen: a control one far from direct anthropogenic stress sources, a pesticide-stress site and multi-stress one, adding to the exposure to pesticides the presence of an electric and magnetic field from a high-voltage power line. The distance between the two sites was about 300 m (near enough to be exposed by foraging activities to the same exposure to pesticides, but sufficiently distant to be differently exposed to the electric and magnetic fields). In each experimental site (control, pesticide- and multi-stress), four colonies of honey bees were used. Apiaries were monitored weekly for one year.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuously

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Exposure duration continuously
Exposure setup
Exposure source
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 1,250 V/m - - - at hive level below the high-voltage power line
magnetic flux density 1.49 µT mean - - ± 0.65 µT (standard deviation)
magnetic flux density 2.43 µT - - - mean daily peak ± 0.97 µT (standard deviation)

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • during exposure

Main outcome of study (acc. to author)

The data showed that bee health conditions were the worst in the multi-stress site (pesticide exposure and exposure to electric and magnetic fields) with only one colony alive out of the four colonies present at the beginning. In this site, a complex picture of adverse effects was observed, such as disease appearance (American foulbrood), higher mortality, behavioral alterations (queen changes, excess of honey storage) and biochemical anomalies (higher alkaline phosphatase enzyme activity at the end of the season).
Even if this study did not allow for testing of the synergistic vs. additive effect of the multi-stress conditions, as single stress was only tested for pesticide-stress, the authors suggest that at least additive effects can be defined for the multi-stress condition investigated.
In conclusion, the results indicate that the multi-stress condition was able to induce biochemical, physiological and behavioral alterations which severely threatened bee colony survival.

Study character:

Study funded by

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