Search

Abstract Background The globose scale (GS), Sphaerolecanium prunastri (Boyer de Fonscolombe) (Hemiptera: Coccoidea), has invaded wild apricot forests in their native range in Central Eurasia threatening the ancestral germplasm resource. Biological control efficacy of the harlequin ladybird, Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) against the globose scale was assessed in laboratory and field experiments. Results In the laboratory, Harmonia axyridis has a high feeding capacity on GS with numbers consumed daily increasing with temperature (15, 20, 25, 30, 35 °C), reaching an upper asymptote of 160–200 scales per day. In field cage experiments, efficacy of biological control (EBC) against first instar (49–99%) and second instar nymphs (20–80%) increased with GS density. When ants were present, control efficiency was reduced by 10–15%. In open-field experiments without cages, EBC was comparatively lower regardless of duration and how H. axyridis were released whether as adults, eggs cards or a mixture of adults and eggs cards. Conclusions In the long term, biological control with this ladybird predator could be considered as part of an IPM program package that includes banning or delaying mowing grass and understory plants in the forests that offer pollen and nectar for natural enemies.

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.