Song, B.Z., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Wu, H.Y., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Kong, Y., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Zhang, J., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Du, Y.L., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Hu, J.H., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China
Yao, Y.C., Department of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China

Five aromatic plants, Centaurea cyanus, Saturela hortensis, Nepeta cataria, Agerarum houstonianum, and Ocimum basilicum, were assessed as intercrops in a pear orchard, and all significantly reduced the pest population compared with that in the plot natural grasses. The decrease was particularly marked for C. cyanus, S. hortensis, and A. houstonianum, and plots intercropped with these aromatic plants also had significantly higher values of ratios of natural enemies to pests, Simpson's index, the Shannon-Wiener index, and the evenness index of arthropod species at the flowering, immature-fruits, and fruit-growth stages of the pear trees. In none of the plots except that intercropped with C. cyanus, however, were there any significant changes in the abundance of predators and parasitoids. Intercropping with aromatic plants in pear orchards proved beneficial to the main crop by repelling pests and regulating the structure of the arthropod community in the pear orchard ecosystem. © 2010 International Organization for Biological Control (IOBC).