Effect of temperature on predation by Harmonia axyridis (Pall.) (Coleoptera: Coccinellidae) on the walnut aphids Chromaphis juglandicola Kalt. and Panaphis juglandis (Goeze)

Abstract

Abstract Background The walnut aphid species Chromaphis juglandicola Kalt. and Panaphis juglandis (Goeze) are destructive insect pests. Harmonia axyridis (Pall.) (Coleoptera: Coccinellidae) is the main predatory insect with a wide geographical distribution. The feeding behavior of the predator against the two different aphid species might influence bio-control efficacy in walnut orchards. Main body Functional response of H. axyridis to various densities of the two aphid species was examined under temperatures ranging from 15 to 30 °C. The results showed that functional responses of H. axyridis towards C. juglandicola or P. juglandis fitted well with the Holling-II equation within the range of 15–30 °C. A greater biomass of aphids was consumed when the temperature increased from 15 to 30 °C. The predation efficacy of H. axyridis against C. juglandicola was greater than against P. juglandis, and the searching efficiency of H. axyridis against C. juglandicola was more effective than against P. juglandis. Moreover, predation rates against both aphid species decreased with increasing the H. axyridis density. Conclusion This study showed that H. axyridis was an effective predator against the two walnut aphids. Increasing temperature (15–30 °C) increased prey consumption. Interference between individuals from increasing predator density had a negative impact on predation rate against the two aphid species.