Abstract
BackgroundThe 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 bodyFunctional 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.ConclusionThis 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.
Highlights
The walnut aphid species Chromaphis juglandicola Kalt. and Panaphis juglandis (Goeze) are destructive insect pests
The objective of this study was to determine the effect of temperature on the functional response of H. axyridis against C. juglandicola and P. juglandis of different densities and at different temperatures
Functional response: predation by H. axyridis on aphids at various densities and four temperatures The functional response of H. axyridis was determined by offering varying densities of 2nd/3rd instar nymphs of each aphid species separately on a walnut leaf disc placed in a Petri dish (90 mm by 18 mm) lined on the base with moist filter paper
Summary
The walnut aphid species Chromaphis juglandicola Kalt. and Panaphis juglandis (Goeze) are destructive insect pests. The small walnut aphid, Chromaphis juglandicola Kaltenbach and the large walnut aphid, Panaphis juglandis Goeze (Hemiptera: Aphididae), are distributed mainly in temperate regions and are destructive pests in walnut orchards in Xinjiang Uygur Autonomous Region, northwestern China (Xing et al 2018). Panaphis juglandis typically feeds along the midrib of the upper surface of the leaves These two species are not usually found together on the same tree in the Kashmir valley, India (Wani and Ahmad 2014a, b), while both species commonly coexist at the same orchard in the Yili River Valley in Xinjiang Uygur Autonomous Region (Xing et al 2018). Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is the main Coccinellid species that feeds on walnut aphids in Yili
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