Effect of Imidacloprid Concentrations on Predatory Functional Responses of Orius similis to Frankliniella occidentalis

Purpose To study the effect of imidacloprid on the functional response and searching efficiency of Orius similis.

Method The imidacloprid mass concentrations of 0.8, 1.6 and 2.4 mg/L and distilled water as control were selected to treat O. similis with the Frankliniella occidentalis densities at 30, 40 and 50 per treatment, respectively, to find out the effect of O. similis on predatory to F. occidentalis under different imidacloprid concentrations.

Result The functional response of O. similis to F. occidentalis was consistent with the Holling II disc equation under the influence of these three imidacloprid concentrations. The difference in predation of O. similis had a certain relationship with the concentration of imidacloprid, that is O. similis predation number was significantly lower in the imidacloprid concentration at 2.4 mg/L than that on control especially in the prey density at 50 (P<0.05). Compared with the control, the control and searching efficiency ofO. similis to F. occidentalis was decreased under the influence of imidacloprid, and the effect of imidacloprid concentration at 0.8 mg/L was not significant (P>0.05), however, the control effect and the finding effect ofO. similis to F. occidentalis were significantly reduced (P<0.05) when the concentration of imidacloprid was at 1.6 mg/L and 2.4 mg/L.

Conclusion Imidacloprid had a negative effect on the number and functional response of O. similis predator to F. occidentalis. The predation number and control effect of O. similis to F. occidentalis decreased under the lower concentrations of imidacloprid.