[Effects of wheat-oilseed rape or wheat-garlic intercropping on the population dynamics of Sitobion avenae and its main natural enemies].

Sitobion avenae (Fabricius) is one of the most important pests of winter wheat in China. An investigation was conducted at the experimental farm of Shandong Agricultural University to study the effects of intercropping oilseed rape or garlic with winter wheat on the population dynamics of S. avenae and its main natural enemies. The results showed that in most cases, the population density of S. avenae apterae was significantly lower in wheat-oilseed rape and wheat-garlic intercropping fields than in wheat monoculture field. The population density of ladybeetle and the ratio of ladybeetle to S. avenae were higher in wheat-oilseed rape intercropping field. Before May 2, the population density of aphid parasitoids in wheat-oilseed rape intercropping field was higher than that in wheat-garlic intercropping field and wheat monoculture field; and after May 5, the mummy rate of aphid parasitoids and the ratio of aphid parasitoids to S. avenae in wheat-oilseed rape intercropping field were significantly higher than those in the other two fields. In wheat-garlic intercropping field, S. avenae alatae had a higher population amount, but no significant change was observed in the population amounts of ladybeetle and aphid parasitoids. It was concluded that wheat-oilseed rape or wheat-garlic intercropping could control S. avenae in wheat fields.

[Effects of wheat synomones on Macrosiphum avenae and its natural enemies].

An investigation was made in winter wheat fields to study the effects of applying wheat synomones methyl salicylate and sulcatone (6-methy-5-hepten-2-one) on the dynamic changes of Macrosiphum avenae and its natural enemies Harmonia axyridis and Aphidius avenae. The results showed that wheat synomones didn' t change the population dynamics of M. avenae significantly, but had a significant effect on the reduction of M. avenae population number. The synomones could deteriorate the existent environment of M. avenae, and make the number of alatae increased obviously. Although synomones decreased the species richness, diversity index, and evenness of natural enemy communities, the numbers of dominant natural enemy species such as A. avenae and H axyridis were increased. Applying wheat synomones was helpful to the control of M. avenae in winter wheat fields.