Ecological Roles Of Volatile Semiochemicals Induced By Wheat Aphid Feeding To Sitobion Avenae In Wheat Fields

The English green aphid Sitobion avenae is the major pest of wheat in China and many other countries. It is not only as a vector of plant virus diseases, but also making heavily damage to wheat. Aphid induced volatile semiochemical is a kind of herbivore-induced plant volatiles (HIPVs). Laboratory study showed that aphids, through their close association with plants, causing systemic release of induced volatile semiochemicals had negative effects on subsequent aphid colonization and could also have positive roles with insects that are antagonistic to aphid development. However, so far, no experiments have been done in winter wheat fields by using volatile semiochemicals induced by wheat aphid feeding, let alone on different resistant cultivars (lines). This paper investigated the ecological roles of the two kinds of volatile semiochemicals induced by wheat aphid feeding methyl salicylate and sulcatone (6-methy - 5- hepten- 2-one) to S. avenae in different resistant wheat cultivars (lines). The main results are as follows:1. Effects of volatile semiochemicals induced by wheat aphid feeding on population dynamics of S. avenae and its natural enemies and on the community structure of the natural enemies.Two kinds of volatile semiochemicals, methyl salicylate and sulcatone were field-tested for the effects on the population dynamics of S. avenae and its natural enemies Harmonia axyridis and Aphidius avenae and on the community structure of the natural enemies in winter wheat fields. The trends of population dynamics of S. avenae in the volatile semiochemicals treated blocks were as the same as these in the control blocks, but the number of S. avenae apterae was reduced significantly in volatile semiochemicals treated blocks. Volatile semiochemicals could deteriorate the existent environment of S. avenae, so more alatae were produced than control blocks. Although the species richness, the index of diversity of community and evenness of natural enemies in volatile semiochemicals treated blocks decreased, the number of the dominant natural enemy species such as A. avenae and H axyridis were increased. Above all, volatile semiochemicals had significantly efficiency to control S. avenae in winter wheat fields.2. Effects of different resistant wheat cultivar (line) and volatile semiochemicals induced by wheat aphid feeding on S. avenae and the parasitoid A. avenaeTwo kinds of volatile semiochemicals methyl salicylate and sulcatone and four wheat cultivars (lines) with different resistant level to S. avenae were field-tested for the effects on S. avenae and its parasitoid A. avenae in winter wheat fields. The apterae density of S. avenae reduced significantly by using methyl salicylate and sulcatone in each wheat cultivar (line), but the alatae density did not. The density of S. avenae alatae increased significantly in methyl salicylate treated blocks. In addition, the number of the parasitoid A. avenae and the parasitic rate increased significantly in semiochemicals treated blocks. Moreover, when volatile semiochemicals were not used, the density of S. avenae and A. avenae and the mummy rate were KOK