Effect of single and mixture of insecticides on earthworms: results from field and laboratory experiments

The aim of this study was to examine the effect of insecticides Talstar 10 EC (pyrethroid bifenthrin) and Nurelle D (mixture of organophosphorus and pyrethroid: chlorpyrifos and cypermethrin) on the life-cycle parameters (survival, growth, cocoons production, and hatching juveniles) of the non-target organism, earthworm Eisenia fetida (Savigny, 1826), in the laboratory and their impact on the natural earthworm population in agricultural field. The experiment was conducted from 2017 to 2019. The field experiment was performed at the Rimski Šančevi site, near Novi Sad, Serbia. The laboratory experiment was conducted according to the OECD guidelines. The earthworms were exposed to the artificial soil supplemented with different concentrations of the tested insecticides according to the recommended agricultural doses (RAD). The mixture of pesticides (Nurelle D) was found ecologically more dangerous to E. fetida than Talstar 10 EC. The 50% lethal concentration (LC 50 ) values of both insecticides were higher than the highest concentration used in the experiment. Talstar 10 EC did not affect weight, but affected the production of cocoons and hatching juveniles, even at the RAD. The mixture of pesticides has shown toxicity after a long-time exposure, and it had an impact on the parameters of the life cycle. The results of the field experiment demonstrated that mixtures of pesticides are more toxic than single-component ones. This points out that the chemicals must be used with the maximum responsibility. Information about long-term effects can be important for understanding the field experiment data, which typically show a high variability and, therefore, are difficult to interpret.