Effects Of Rice-Tobacco Intercropping On Major Pests And The Guild Of Natural Enemies In Rice Fields

Flue-cured tobacco is one of the most important cash crops in China, which is cultivated widely in Wuyi Mt., Fujian Province. In accordance with the local conditions that tobacco and early rice have overlap in growing periods, the systems of rice fields neighboring to tobacco habitats were established to investigate the population dynamics of major insect pests and composition, structure and movement dynamics of natural enemies, with the rice monoculture systems as controls. The results are as follows:1 Effects of rice-tobacco intercropping on population dynamics of the major insect pests in rice fieldsThe densities of leaffolder and white-backed planthopper (WBPH) were lower in rice-tobacco intercropping systems than in rice monoculture systems, particularly significantly different in the early growing stage of rice for leaffolders, and significantly different in the late growing stage of rice for WBPHs. The densities of stem borers were not significantly different between the two systems.2 Effects of rice-tobacco intercropping on spider guild structure and its relationship with insect pests in rice fieldsDuring the whole growing period of rice, species richness, individual abundance and Simpson index of spider guild were lower in rice-tobacco intercropping systems than in rice monoculture systems, while Shannon-Wiener index and Pielou index were higher. Ratios of spider abundance to leaffolder abundance and to WBPH abundance were higher in rice-tobacco intercropping systems than in rice monoculture systems in most growing stage of rice, which indicates that rice-tobacco intercropping measure can enhance the capacity of spider to control pests, particularly to control WBPHs.3 Effects of rice-tobacco intercropping on parasitoid guild structure and its relationship with insect pests in rice fieldsDuring the whole growing period of rice, species richness, Shannon-Wiener index and Simpson index of parasitoid guild were higher in rice-tobacco intercropping systems than in rice monoculture systems, while individual abundance and Pielou index were lower. Ratio of parasitoid abundance to leaffolder abundance were higher in rice-tobacco intercropping systems than in rice monoculture systems in most growing stage of rice, while ratio of parasitoid abundance to WBPH abundance were higher on several sampling dates, which indicate that rice-tobacco intercropping measure can enhance the capacity of parasitoids to control pests, particularly to control leaffolders.4 Effects of rice-tobacco intercropping on movement of predator enemiesDuring the early growing season of rice, predatory ground-dwelling beetles inclined to migrate from tobacco fields to rice fields, while in the late growing season the movement direction was converse. Spiders in the whole season tended to migrate from tobacco fields to rice fields. The results indicate that tobacco habitats can function as species pool and source of predatory natural enemies.