| The English grain aphid Macrosiphum avenae is one of the most prominent agricultural pests in wheat product, which results in serious wheat lost in China. By using combining methods of field observation, artificial simulation and indoor laboratory analysis, interference of population development of Macrosiphum avenae by meteorological factors such as wind and rain was studied. And it was analysed that characteristics of population development and recovery interfered by wind and rain in different intensity during different stages of population development or different phenological periods of host species. Meanwhile, critical period of aphid population development affected by the wind and rain was cleared. At the same time, main mechanism of aphid population decrease interfered by the wind and rain was observed indoors.In terms of field experiments, critical period of aphids damage control was explicit. Undoubtedly, it provided new idea with harmless control of wheat aphids and wheat green production.(1) The results from systematic observation and analysis from 2006 through 2008, demonstrated that meteorological factors such as wind and rain were essential for population development of English grain aphid. For example, a gale suppressed 65 percent of the population growth; the rainfall lasting 10 hours (daily rainfall was 32.2mm) led to 80% of significant decrease of aphid population.(2) The simulating experiment of wind blow and water spray in the wheat field showed that with increased intensity and duration of treatment, there was an increase in decline rate. In fact, the decline rate of aphid population was above 70%, which handled by 15～18.3 m/s average wind speed of motorized sprayer (dynamic stall was 5 gears or 6 gears) with 20~30 s/m2 and 52.5 mm spray of motorized duster with 3～6 min. At the same time, the appropriate intensity and treatment time of wind blow and water spray in the field was determined. In addition to, medium-caliber spray of motorized sprayer with 1～3 min/m2 could get a better control effect.(3) Control effect of aphid population on the flag leaf of wheat was apparently higher than the one on the ear of wheat; control effect on winged aphid populations was much higher than non-winged aphid; control effect on target spraying was obviously higher than non-target spraying. Meanwhile, under the condition of the appropriate treatment intensity of wind blow and water spray, there was no significant effect on the dominant species of natural enemies in wheat field including Coccinella septempunctata, Harmonia axyridis and Prapylaea japonica. But there was certain effect on parasitoid wasps (Aphidius avenae and Aphidius gifuensia).(4) According to the control effects on M. avenae by the same treatment of water spray and wind blow during different wheat growth stages, it was determined that the early filling stage of wheat was the best period for artificial water spray and wind blow. It meant that disposable treatment on this phase would gain the ideal control effect and maintain the wheat grain weight.(5) Measure comparison of field simulating experiment with mesh hood and without mesh hood, showed that with increased duration, there was persistent decrease of population within the mesh hood in the middle filling stage of wheat. Finally, under the control of the natural enemies, aphid populations were completely eliminated. However, under the condition without mesh hood, population density interfered by spray would slow recovery. It meant that the population density at 7 days after treatment was equivalent to the rest of population at the day after treatment.(6) Indoor observation on main mechanism of population density decrease interfered by the wind and rain displayed that aphid alarm pheromone produced by the interference, stylet fractured and body damage made the population number decreased. However, the body damage was the most important impact factor. |
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