Abstract:

Referring to the push-pull theory and biodiversity protection strategy, the ecological regulation technology targeting alfalfa thrips was studied through field systematic monitoring of arthropods in fields intercropped alfalfa with different functional plants, such as Lotus corniculatus, Onobrychis viciifolia, Trifolium repens, Coronilla varia, and Tanacetum cinerariifolium in different proportions. The results showed that the population size of thrips and natural enemies Orius similis in alfalfa fields before harvest was significantly higher than that in corresponding intercropping functional plant areas. One week after mowing, the population density of O. similis in the alfalfa fields intercropped with L. corniculatus, O. viciifolia, T. repens, and T. cinerariifolium decreased significantly, while the density of O. similis in the corresponding functional plant area increased significantly. The density of O. similis in the three functional plant areas of L. corniculatus, O. viciifolia and T. repens increased from 3.67, 3.00, and 3.67 insects/10 double nets before cutting to 11.50, 29.17, and 15.00 insects/10 double nets at one week after mowing, respectively, which represented increases of 3.13 times, 9.73 times and 4.09 times , respectively. Thrips population density in alfalfa field decreased significantly, corresponding to different changes in thrips density in different functional plant areas, and increased significantly in L. corniculatus and T. repens, but there was no significant difference between other areas and before mowing. At 2 weeks after cutting, the population density of thrips increased significantly with the regeneration of alfalfa, the density of O. similis in each functional plant area decreased significantly but increased significantly in the alfalfa fields. At 3―4 weeks after cutting, the density of O. similis decreased significantly with the decline of thrips population density in alfalfa fields, and the population density of O. similis and thrips in different functional plant areas did not change significantly. The strength of regulation effect of alfalfa intercropping with 5 functional plants at a ratio of 4:1 on thrips ranks from high to low: T. repens, T. cinerariifolium, O. viciifolia, L. corniculatus, C. varia. The study serves as a reference for protecting the natural enemies of alfalfa field ecosystem to provide ecological service.

Key words: alfalfa field, functional plant, intercropping, thrips, Orius similis, ecological regulation