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

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.