The death of honey bees and environmental pollution by pesticides: the honey bees as biological indicators

The monitoring of pesticides with honey bees, which has been carried out by our group since the beginning of the 1980’s, is an extremely important technique not only for proving potential bee poisoning risks by the use of pesticides, but also for determining the degree of environmental contamination due to plant protection products. In fact, because of its morphological and ethological features (such as its wide area of patrol and its intense foraging activity), the honey bee can be considered an excellent bioindicator. In many cases, pollution caused by abuse or by erroneous application of pesticides could not be proven without the help of honey bees. In this research work, which is being applied hitherto in some areas surrounding Bologna, each monitoring station consists of two beehives equipped with collection cages for dead bees. Once a week, families are checked and the number of dead bees is recorded. When the mortality rate exceeds the critical threshold (250 bees/week/station), laboratory analyses are carried out. Monitoring techniques, chemical and palinological analyses, and data processing (through the Environmental Hazard Index) enable us to characterise areas, to indicate periods of major bee poisoning risk, and to identify the most frequently used pesticides (also those that are prohibited) and the crops treated. Our studies with honey bees reveal the type of plant protection management applied to the area under investigation and allow us to prove the application of molecules not permitted under certain circumstances or even forbidden.