Effects Of Intercropping Aromatic Plants On Arthropod Community In Apple Orchard

The interaction relations of habitats,plants,pests and natural enemies are the theoretical basis and research focus of integrated pest management in orchard ecocystem.In the present study,we selected four aromatic plants,namely Mentha Canadensis L.,Agerarum houstonianum Mill.,Tagets patula L.and Ocimum basilicum L.,were assessed as intercrops in an apple orchard,and natural grasses as control to analyse the effects of intercropping aromatic plants on the composition and temporal dynamics of arthropod communities and the correlations of dominant pests and its natural enemies.We found that arthropods collected from the orchards could be classified into 12 orders,49 families and 73 species.The dominant pests are Aphis citricola Van der Goot,Toxoptera piricola Matsumura,Myzus malisutus Matsumura,Eriosoma lanigerum(Hausmann),Choristoneura longicellana Walsingham,Spilonota lechriaspis Meyrick and Adoxophyes orana Fisher,and the dominant natural enemies are Coccinella septempunctata L.,Leis axyridis Pallas,Propylaea japonica Thunberg,Encyrtidae spp.,Trichogrammatidae spp.,Braconidae spp.,Ichneumonidae spp.,Chrysoperla sinica Tjeder,Chrysopa formosa Brauer,Epistrophe balteata De Geer and Syrphus corollae Fabricius.Intercropping aromatic plants had significantly reduced herbivore individual number,herbivore numbers declined by 31.59%、25.40%、29.08%和16.40%in plots intercropped with Mentha Canadensis,Agerarum houstonianum,Tagetes patula and Ocimum basilicum,respectively.Compared with natural grasses plot,herbivore species richness declined by 11.6%on average in plots intercropped with aromatic plants.By contrast,predator numbers in intercropped plots were significantly higher than natural grasses plot,except for plots intercropped with Mentha canadensis,and predator numbers increased by 18.78%on average.The species richness of predators also significantly increased of 15.6%on average in plots intercropped with aromatic plants.Intercropping with aromatic plants also affected the dynamics of herbivore,predator abundance and species richness,and significantly increased the ratio of predator abundance to herbivore abundance and the ratio of predator richness to herbivore richness.Intercropping also shortened the occurrence duration and depressed the incidence peak of the pest sub-community.Equally important,intercropping significantly increased the dominant natural enemies of apple yellow aphid individual number in flowering period,and enhanced the relationship of apple yellow aphid and its natural enemies,then significantly reduced apple yellow aphid populations.Our results demonstrate that intercropping with aromatic plants in apple orchards can greatly enhance the role of the natural enemies biological control pests,decrease herbivore numbers and species richness by the repellent effects of aromatic plants and highten the relationship of the dominant pests and that’s natural enemies,shift a herbivore dominated trophic structure to a predator dominated one,and led to a considerable improvement in arthropod pest management within the apple orchard ecosystem.