Effects of the Modern Biorational Insecticide Spinosad on the Earthworm Eisenia fetida (Savigny, 1826) (Annelida: Clitellata)

Abstract

Effects of the biorational insecticide spinosad on the life-cycle parameters (survival, growth, cocoon production and hatching juveniles) of a non-target organism, the earthworm Eisenia fetida, were examined. An artificial soil supplemented with different concentrations of the examined insecticide based on the recommended agricultural doses (RAD) was used. The laboratory test was conducted according to the OECD guidelines. Our results showed that the insecticide spinosad had no impact on the earthworm mortality. However, for four weeks assessment, the insecticide effects on weight were significant when applying 4×RAD. At the sixth week of the assessment, the insecticide effects were significant in RAD, 2×RAD and 4×RAD. After eight weeks, statistical analyses revealed a significant difference in all concentrations (except in the lowest concentration ¼RAD) compared with the control. A negative growth inhibition was observed in the ¼RAD, ½RAD and RAD during the four-week experiment. A positive growth inhibition was observed in all other weeks and concentrations. The results of cocoon production and hatching juveniles showed no significant difference between the control and the treatments. The results showed statistically significant impact on the weight after a long-term exposure, even in a concentration smaller than recommended.