National Projects
Project duration: 
Jan 2019 to Dec 2021

The aim of this study is to understand how exposure to mixtures of pesticide residues affects orchard pollinator populations. 


Declines in wild bee diversity and abnormal honeybee colony losses have been reported worldwide. Notwithstanding other factors, pesticides are considered one of the main drivers of these declines. Before being authorized for commercial use, pesticides undergo a stringent risk assessment process. Therefore, assuming risk assessment schemes are adequate, bee poisoning incidents should be rare. Yet, bee poisoning events are by no means uncommon in agricultural environments. During our studies on the management of the solitary bee Osmia cornuta as an orchard pollinator we have observed the disruption of  foraging and nesting activities following pesticide sprays. In parallel, we have conducted laboratory studies demonstrating synergistic effects between sublethal doses of insecticides and fungicides. Our hypothesis is that the sublethal effects observed in commercial orchards are caused by the mixture of fungicides sprayed during bloom and background residues of insecticides applied before bloom. 

We will use the solitary bee Osmia cornuta as a model species. We have the following objectives: 1) To document multiresidue pesticide levels in the pollen and nectar of fruit tree flowers in commercial orchards; 2) To test the hypothesis that certain mixtures of fungicides and low sublethal levels of insecticides disrupt foraging and nesting behaviour of solitary bees; 3) To analyse the effects of orchard management (IPM vs organic) on O. cornuta population dynamics and pollination services; 4) To design laboratory, cage and field pesticide risk assessment protocols for solitary bees. 

Proyecto RTI2018-098399-B-I00 financiado por MCIN/ AEI /10.13039/501100011033/ y por FEDER Una manera de hacer Europa


In this project we will conduct laboratory, cage (semi-field) and field experiments in which O. cornuta individuals/populations will be exposed to mixtures of pesticides at field-relevant doses. We will measure the effects of these exposures on loss of olfactory capacity, flower visitation rates, reproductive success and population dynamics. Our project has important environmental consequences for the conservation of both managed and wild pollinators. Our project also has important consequences for the fruit industry. The disruption of foraging and nesting activities results in a reduction of pollination services, potentially affecting fruit production. Finally, our project has profound consequences for pesticide regulation. The eventual confirmation of our hypotheses would imply that current risk assessment schemes are inadequate to protect bee populations and should be profoundly revised.