Pesticides in the honey bee colony

The INSIGNIA-EU project explores the pollution status of the environment in the proximity of an apiary. It uses the honey bee colony as a convenient sampling tool, because the pollutants found on bees and bee products reflect the pollution status around the apiary, which is an area of about 13 km² based on a cautious flight range of 2 km, and about 30 km² assuming the bees collect their food within a 3 km flight radius. In the earlier INSIGNIA-bee study (2018-2021) we found in total residues of 174 different pesticides in the hive. These pesticides were detected using the APIStrip, the in-hive passive sampling device especially created for this study to detect pesticides that circulate in the hive.

What does this tell us?
The simple answer is that there are a large number of pesticides in the environment in locations where they can be collected by the foraging honey bees. But there is more to tell... As these pesticides usually occur in such low concentrations, they are almost impossible to detect, but a bee colony hosts thousands of bees that after foraging leave these undetectable small amounts on the APIStrip. This is a strip coated with special material, the polymer TENAX, which absorbs substances including the majority of pesticide molecules. The APIStrip accumulates the molecules until detectable levels have been reached and the content of the strip can then be analysed in the laboratory.

How do these residues end up in the honey bee colony?
Pesticide distribution follows two routes: the first consists of the direct spraying of crops in the proximity of the hive; and the second route is the indirect dissemination and deposition over long distances of aerosols containing pesticides as a result of spraying and dusting of soils. Looking at the research results, the great majority of the pesticides occur in such small amounts that it is likely to be the result of aerosol deposition and dusting.  

Does this have an acute impact on the honey bee colony?
The amounts of pesticides detected in the apiaries are measured in nanograms, which are a billionth of a kilogram. These very-very small amounts do not cause any direct effect on the health of the bee. It takes about a thousand fold higher amount to show any impact on the bees, as has been shown in laboratory studies.

How do honey bees cope with the pesticide residues?
Nature, so also pollen, is full of toxic substances. For example plants produce toxins to protect themselves from insects that want to eat their leaves and other parts. The evolutionary response was and still is, that in turn these insects, and all other organisms, develop ways to make these toxic substances less or non-toxic. Every organism has various routes for these de-toxification processes, so honey bees can deal with these very small amounts.    

In summary, yes we do find residues of pesticides in the honey bee colony. This is sad but true, because pesticides are widespread and occur also in locations where they have not been applied. As a result, the honey bee colony reflects its environment as every organism, from bacteria to even humans do. In the great majority of the environments sampled within the project, however, the amounts of pesticides found are low and cause no toxicity for bees.

Sjef van der Steen, coordinator INSIGNIA-EU
March 2023