Yao Yuncong

Temporal dynamics of the arthropod community in pear orchards intercropped with aromatic plants.

BACKGROUNDnIncreasing attention has been paid to enhancing biological control through habitat management in agricultural systems for enhanced pest management. Pest management benefits can be realised by intercropping, which can increase natural enemy abundance and, in turn, reduce pest abundance. In this study, the composition and temporal dynamics of arthropod communities in pear orchards when intercropped with aromatic plants were investigated, and the effectiveness and applicability of aromatic plants as intercrops for enhancing insect control were assessed.nnnRESULTSnWhen compared with natural grasses or clean tillage, intercropping significantly reduced pest abundance and increased the ratio of natural enemies to pests. Intercropping also shortened the occurrence duration and depressed the incidence peak in annual dynamics curves of the pest subcommunity and the arthropod community, mainly because of the repellent effects of aromatic plants. Equally important, intercropping significantly reduced the numbers of major pests, such as Psylla chinensis, Aphis citricola and Pseudococcus comstocki, while their incidence period was delayed to varying degrees, and the numbers of their dominant natural enemies (Coccinella septempunctata, Phytoseiulus persimilis and Chrysoperla sinica) increased.nnnCONCLUSIONnIntercropping with aromatic plants led to a considerable improvement in arthropod pest management by enhancing the activity of the beneficial arthropod community within the pear orchard ecosystem.

Intercropping With Aromatic Plants Decreases Herbivore Abundance, Species Richness, and Shifts Arthropod Community Trophic Structure

ABSTRACT n Habitat management is important for the regulation of arthropod community structures to reduce pest populations in orchard ecosystems, but there is limited information on how intercropping with aromatic plants regulates arthropod community structure at trophic levels. We selected four aromatic plants, Mentha canadensis L., Agerarum houstonianum Mill, Tagetes patula L., and Ocimum basilicum L., as intercrops in apple orchard to analyze the effects of intercropping on herbivore and predator abundance, species richness, and to measure the changes of trophic levels of the associated arthropod community. We found that intercropping with aromatic plants, compared with intercropping with natural herb vegetation, significantly reduced herbivore abundance and species richness by 25.62 and 11.6%, respectively. Intercropping significantly increased predator abundance and species richness by 18.78 and 15.6%, respectively, with predator abundance most notably affected during the flowering period of aromatic plants. Furthermore, herbivore abundance and species richness were strongly negatively correlated with predator species richness. Intercropping affected herbivore-predator dynamics, with an observed increase in the ratios of predator abundance and richness to herbivore abundance and richness. Our results indicate that intercropping with aromatic plants in apple orchards may play a role in the observed shift from a herbivore-dominated to a predator-dominated trophic structure, which is likely to have important flow-on effects on arthropod community structure.