Ecological Effects Of Volatile Semiochemicals Induced By Wheat Aphid And Species Diversity On Macrosiphum Avenae

This paper investigated the ecological effects of volatile semiochemicals induced by wheat aphid feeding and species diversity on Macrosiphum avenae and its natural enemies. The main results are as follows:1. Effects of volatile semiochemicals induced by wheat aphid feeding on population of M. avenae and its main natural enemiesTwo kinds of volatile semiochemicals, methyl salicylate and sulcatone were field-tested for the effects on the population of M. avenae and its natural enemies Harmonia axyridis and Aphidius avenae in winter wheat fields in 2006 and 2008. The trends of population dynamics of M. avenae in the volatile semiochemicals treated blocks were as the same as these in the control blocks, but the number of M. avenae was reduced significantly in volatile semiochemicals treated blocks. Mummy rate and the number of H. axyridis and A. avenae were increased in the volatile semiochemicals treated blocks. Above all, volatile semiochemicals had significantly efficiency to control M. avenae in winter wheat fields.2. Effects of wheat-oilseed rape or wheat-garlic intercropping on population of M. avenae and its main natural enemiesIn the study, we intercropped garlic and oilseed rape into wheat in 2007 and 2008 to examine ecological effects of this intercropping system on the population of M. avenae and its main natural enemies. The results showed that the densities of M. avenae were almost significantly lower in wheat-oilseed rape intercropping blocks and wheat-garlic intercropping blocks than wheat monocultures. Mean number of H. axyridis in wheat-oilseed rape intercropping blocks was higher than the other two blocks. The mummy rate in wheat-oilseed rape intercropping blocks was always higher than wheat monocultures. The order of mean number of mummy rate was: wheat-oilseed rape intercropping blocks > wheat-garlic intercropping blocks > wheat monocultures. It was suggested that wheat-oilseed rape or wheat-garlic intercropping could reduce the population densities of M. avenae in agroecosystem.3. Ecological effects of different resistant wheat cultivars and intercropping patterns on M. avenae and its main natural enemies in wheat fieldsThe effects of different resistant wheat cultivars and different intercropping patterns on the densities of M. avenae and its natural enemies were evaluated. Three winter wheat cultivars with different resistant levels to M. avenae were used:'KOK'(high resistance),'JP1'(middle resistance) and'Hongmanghong'(susceptible). The results showed that different resistant wheat cultivars did not change the the trends of population dynamics of M. avenae and its natural enemies caused by intercropping of wheat and oilseed rape or garlic. The mean numbers of M. avenae, Harmonia axyridis and Aphidius avenae on wheat cultivar'Hongmanghong'were all highest. The mean number of H. axyridis in wheat-oilseed rape intercropping blocks was significantly higher than the other two blocks. Comparing with wheat monoculture blocks, wheat-garlic or wheat-oilseed rape intercropping could reduce the mean number of M. avenae. Wheat cultivar'KOK'or'JP1'intercropping with oilseed rape was a better mode.4. Effects of wheat-oilseed rape intercropping and the application of methyl salicylate on population of M. avenae and its main natural enemiesIn the study, we intercropped oilseed rape and applied methyl salicylate into wheat to examine ecological effects on the population dynamics of M. avenae and its main natural enemies. The results showed that the number of M. avenae apterae was significantly lower in the methyl salicylate treated wheat-oilseed rape intercropping blocks than wheat-oilseed rape intercropping blocks from April 25 to May 13, significantly higher from April 25 to May 1 and lower from May 1 to 13 than methyl salicylate treated blocks. The population number of H. axyridis in the methyl salicylate treated wheat-oilseed rape intercropping blocks was higher significantly than wheat-oilseed rape intercropping blocks and methyl salicylate treated blocks. No significant change was observed in the population number of A.avenae between the methyl salicylate treated wheat-oilseed rape intercropping blocks and wheat-oilseed rape intercropping blocks all the time. The mummy rate in the methyl salicylate treated wheat-oilseed rape intercropping blocks was significantly higher than wheat-oilseed rape intercropping blocks and methyl salicylate treated blocks from May 7 to 16. It was suggested that combined effects are better than single effects of wheat-oilseed rape intercropping or application of methyl salicylate.