Effects of wheat-pea intercropping on the population dynamics of Sitobion avenae (Homoptera: Aphididae) and its main natural enemies

To study the ecological regulation effects of species diversity in wheat fields on Sitobion avenae, field experiments were carried out in Langfang Experimental Station of Institute of Plant Protection, Chinese Academy of Agricultural Sciences from October of 2007 to July of 2008. The intercropping patterns of wheat and pea, by the proportion of planting row of pea and wheat in 2:2, 2:4, 2:6 and 2:8, were plotted, and the field cultivar monoculture of wheat was planted as the control. Population dynamics of apterae and alatae S. avenae, population dynamics, species richness, diversity index and evenness of main natural enemies were investigated systematically and analyzed. The results showed that, compared with monoculture of wheat, the amount of S. avenae apterae per 100 plants (square-root transformed) in aphid peak period were very significantly lower in the intercropping treatments (P<0.01), and the cascade was that wheat monoculture (77.38) > 2-2 intercropping (68.62) > 2-4 intercropping (68.51) > 2-8 intercropping (65.19) > 2-6 intercropping (64.94). Although population dynamics of main natural enemies showed a similar trend with time, wheat-pea intercropping could preserve and augment natural enemies more than monoculture of wheat, and there were higher population densities of ladybeetles and aphid parasitoids, and higher species richness and diversity index of natural enemies, but lower evenness index in each intercropping field. It is so concluded that wheat-pea intercropping system can not only reduce the population of S. avenae, but also improve the stability and sustainability of controlling wheat pests.