The interaction among Psylla chinensis and natural enemies in the different aromatic plants intercropping plots of pear orchard
梨园芳香植物间作区中国梨木虱与其天敌类群的相互作用

To evaluate effects of intercropping aromatic plants on the interactions among Psylla chinensis and its natural enemies in pear orchard, the composition, population dynamics, time niche of P. chinensis and its natural enemies in different intercropping regions were investigated and analyzed by grey relational grade method during the annual growth cycle of pear. The results showed that there were obvious differences among the frequency, composition, timing characteristics, breadth and overlap of time niche in the different aromatic plant treatments. In the Mentha haplocalyx (Briq. var. piperascens Malinvaud) region the time niche breadth of P. chinensis and its most of natural enemies were larger than that in clean tillage (CK). Occurrence quantity distributed evenly without an obvious peak. The overlap indices were also greater than that of CK with the phenomenon of synchronization and following performance. In the intercropping Tagetes patula L., Ocimum basilicum L., and natural grass regions, the time niche breadth of P. chinensis was relatively smaller comparing to that in the intercropping Mentha haplocalyx (Briq. var. piperascens Malinvaud) region with an obvious peak, but time niche breadth of natural enemies was greater than CK and without peak. Some natural enemies species, Encyrtidas, Chrysopa perla, Braconids, and Ichneumonids etc., showed synchronization following performance obviously with P. chinensis rather than Harmonia axyridis, Coccinella Septempunctata Linnaeus and Chrysopa stnica Tjeder. The results of grey relational analysis that it has a greater effect on P. chinensis than other species that the Encyrtidas in the intercropping Mentha haplocalyx (Briq. var. piperascens Malinvaud) region, the Ch. stnica Tjeder in the intercropping T. patula L. region, the Propylaea Japonica (Thunberg) and Ch. stnica Tjeder in the intercropping H. axyridis region, the Ch. perla, Braconids and Trichogrammatids in the natural grass area. Therefore, intercropping aromatic plants in the pear orchard may control the occurrence of P. chinensis through improving the group composition, timing characteristics and niche character of the pest and their natural enemies.