Browsing by Author "Ge, F."
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- ItemEffects of inter-annual landscape change on interactions between cereal aphids and their natural enemies(Elsevier, 2013) Zhao, Z.H.; Hui, C.; Ouyang, F.; Liu, J.H.; Guan, X.Q.; He, D.H.; Ge, F.The agricultural intensification and the subsequent habitat changes in agroecosystem can strongly affect biological control services. We here examine the influence of inter-annual landscape change in wheat field area on interactions of cereal aphids and their natural enemies, as well as the efficacy of biological control using data collected from a 4-year experiment in Northwest China. Two hypotheses were tested. (i) Population densities decline following an inter-annual expansion of wheat crop proportion cover due to dilution and crowding effects. (ii) Species that are specialists or at higher trophic levels are more sensitive to bottom-up disturbance by inter-annual change in percent cover of wheat crop. Results showed the population densities of one cereal aphid (Macrosiphum avenae), one parasitic wasp (Aphidius avenae), two specialist predators (ladybirds: Hippodamia variegata and H. tredecimpunctata) and one hyperparasitic wasp (Pachyneuron aphidis) declined following the expansion of wheat crop areas, supporting the predictions of inter-annual dilution and crowding effects. In contrast, the populations of one cereal aphid (Schizaphis graminum), one parasitic wasp (A. gifuensis), two generalist predators (spiders: Pardosa astrigera; carabid beetles: Chlaenius pallipes), and two hyperparasitic wasps (Asaphes suspensus, and Alloxysta sp.) did not respond to inter-annual landscape change. The two hypotheses were partially supported but with noticeable exceptions, and the bio-control efficiency declined with the increase of the proportion cover of wheat field in agricultural landscape. Overall, different responses of cereal aphids and their natural enemies make it difficult but still possible to optimize inter-annual landscape change for enhancing the parasitism rate and predator-prey ratio.
- ItemEffects of position within wheat field and adjacent habitats on the density and diversity of cereal aphids and their natural enemies(2013) Zhao, Z.H.; Hui, C.; He, D.H.; Ge, F.The spatial structure of agricultural land- scapes can have a strong impact on the distribution and diversity of insects. Here we studied the effects of within-field position (edge or center) as well as adjacent habitats on the community structure of the natural enemies of cereal aphids. Twelve agricultural sites were included in the study, with two spring wheat fields selected for each site (one adjacent to an alfalfa field, the other adjacent to a corn field). We sampled two rows per field (1 and 20 m from the edge) using pitfall trapping for ground-dwelling predators, sweep netting for leaf- dwelling predators and hand collecting of aphid mummies for parasitoids. Adjacent alfalfa areas, as opposed to corn fields, can significantly increase the abundance and diversity of leaf-dwelling predators and parasitoids near the field edges. Abundance and diver- sity were found significantly higher near the edges than in the centers of fields adjacent to alfalfa areas. In contrast, no significant differences were found between edges and centers of fields adjacent to corn fields. Of the fifteen most abundant species, Aphidius avenae (Hali- day), A. gifuensis (Ashmead), Hippodamia variegata (Goeze) and Chrysopa sinica (Tjeder) were significantly more abundant near the edge than in the center. Being adjacent to alfalfa habitats could enhance parasitism and predator/prey ratios of leaf-dwelling predators at the edges, but has no effects on ground-dwelling predators. In conclusion, the effect of within-field position and adjacent habitats on natural enemies of agricultural pests was species specific. This should be considered for designing efficient plans of biological control.
- ItemPlant species richness controls arthropod food web: Evidence from an experimental model system(Oxford University Press on behalf of Entomological Society of America, 2019) Zhao, Z.-H.; Hui, C.; Reddy, G.V.P.; Ouyang, F.; Men, X.-Y.; Ge, F.The effects of plant species richness on the function and stability of ecosystems have been an area of focus in recent decades. Arthropod community is one of the most important components in agroecosystems and can provide multiple ecosystem services, including biocontrol and pollination. In particular, species composition and biocontrol function can be sensitive to changes in plant species richness. Here, we designed 50 plots with five levels of plant species richness to examine arthropod distribution and composition over 4 yr. Arthropod richness was found to be positively correlated with plant species richness. High plant species richness can enhance the temporal stability of the arthropod community but can also lead to a decline in the population stability of some species. The species richness and biomass of environmentally friendly insects (EFI), such as honeybees, ants and flies, were found to be positively correlated with those of the natural enemies. As such, high levels of EFI could sustain food web robustness by serving as alternative prey/hosts for natural enemies. The mediation of EFI in the interaction between crops and pests has implications for successful biocontrol practices using natural enemies. Planting diverse plant species with a certain level of spatial turnover could benefit the biocontrol function of natural enemies and safeguard multiple ecosystem services.