The Ecological Regulation And Mechanism Of The Intercropping Of Wheat And Two Fabaceous Crops On English Grain Aphid And Its Enemies

English grain aphid (Sitobion avenae) is the major pest of study in this thesis. Systemic investigation of wheat/bean intercropping field were combined with the detection of olfactory response of aphids and its enemies to the phyto-infochemicals in laboratory, the ecological regulation of crop diversity to S. avenae were comprehensive evaluated. The main research results are as follows:To evaluate the effect of wheat (Triticum aestivum L.) /mung bean (Vigna radiate) intercropping on populations of English grain aphid and its natural enemies. Wheat and mung bean intercropped were designed by the following different row ratios: 10: 10 (10W: 10MB), 12: 6 (12W: 6MB), 12: 4 (12W: 4MB), 16: 4 (16W: 4MB), as well as wheat monoculture control. Population quantity of S. avenae and its enemies had been sampling surveyed when the aphid loading on the wheat seeding. Temperature, humidity and wind speed also were monitored by the microclimate observation apparatus. The results showed that the trend of aphids and its enemies'population dynamic with time could not be affected by wheat/mung bean intercropping in different row ratios, but could strongly influence the population quantity dynamic change of S. avenae. Compared with the wheat monoculture, the patterns of intercropping 12W: 4MB and 16W: 4MB had significantly decreased apterae aphids population on wheat; 12W: 6MB and 12W: 4MB had significantly decreased alatae aphid population during the sampling period and the aphid peak time. At the same time, the quantity and species of enemies were enhanced by intercropping, index of dispersion for all intercropping patterns were lower than that in wheat, mean crowding index of aphids in intercropping patterns changed with the quantity of S. avenae, the highest of that was monoculture, the lowest was 12W: 4MB during the peak time. Gathered degree for monoculture was higher, which indicated by L and CA of aphids. The value ofβi?n Iwao regression equation for 16W: 4MB was higher than other disposes. Intercropping improved the wind speed and temperature, reduced relative humidity in wheat field. The microclimate elements of changed more for 16W: 4MB than other treatments. The average temperature with the highest temperature or relative humidity were significant correlation.Temperature and number of aphids were negative correlation before peak time of aphids.To evaluate the ecological regulation of wheat intercropping with mung bean or pea to S. avenae population, a comparision experiment was designed by row ratio16: 4 in the field to investigate the quantity and dynamic changes with time of S. avenae population. Selective preference of S. avenae to the volatile of wheat, mung bean, pea and their different combination were analysed by Y-tube set in laboratory test. Results showed that compared with the monoculture, the quantity of aphids was significantly decreased in intercropping fields. Olfactory response experiment showed that the odour of host were significantly selected by S. avenae apterae and alatae, the mixture odour of wheat with mung bean or pea had no appeal to the aphid. The odour of non-host could cover the odour of host, which interferred the aphid's host location, this phenomenon maybe one of reasons that quantity of aphids populations in intercropping field was lower than monoculture. Four-arm olfactometer had been used to tested olfactory response of S. avenae and lady beetle (Harmonia axyridis) to 4 kinds of phyto- infochemical (Methylsalicylate, Z-3-hexen-1-ol, Z-3-hexeyl acetate, 1-hexanol) in 3 doses (1, 10, 100μg/mL). Wind tunnel for the hoverfly (Episyrphus balteatus) to 4 volatiles in 1000μg/mL and aphids. The results showed that Z-3-hexeyl acetate in 3 doses and 1-hexanol in 10, 100μg/mL significantly attracted S. avenae. But the aphids spent shorter time in dispose arm, with the increasing dose of Z-3-hexeyl acetate. The higest dose of 4 volatiles significantly appealed to H. axyridis. Z-3-hexeyl acetate and aphids could cause searching behavior of E. balteatus. So the high concentration of methylsalicylate, Z-3-hexen-1-ol and Z-3-hexeyl acetate attracted more to natural enemies. Based on the above results, the function of plant volatiles that do not attract aphids and appealed enemies provides a theory basis for slow releaser preparation and application prospects for plant volatiles, then to develop push-pull strategy for wheat aphids control.