The Effects Of Long-term Different Intensity Of UV-B Radiation On The Ecological Parameters And Feeding Behavior Of Sitobion Avenae (Fabricius)(Hemiptera: Aphididae)

The environmental deterioration has become more and more serious with the start andthe development of modern industry, and even caused the emerging of the Antarctic ozonehole. Consequently, the amount of UV-B radiation was enhanced in our environment. Toomuch UV-B radiation provided selective pressure for the creature on the earth to some extent,and could affect the creatures’ hereditary and evolution. The indirect and direct influence ofdifferent intensity of UV-B radiation on the Sitobion avenae (Fabricius) were studied throughthe wheat and the aphids themselves exposed under UV-B. And the EPG and life table wereemployed for this study to provide some theoretical basis for the insect ecology and practiceof pest control. The results are the followings:1. The indirect effect of different intensity of UV-B radiation on Sitobion avenae(1) The effects of wheat exposed under UV-B radiation on the ecological parameters of S.avenaeThe result indicated that life table parameters such as the intrinsic rate of increase (rm), the netrate of increase (R0), fecundity (F) and the mean length of a generation (T) of S. avenaefeeding on the wheat exposed under high intensity (0.75mW/cm2) of UV-B radiation declineddramatically with significant differences. The corresponding parameters tested with lowintensity (0.2mW/cm2) UV-B radiation were basically identical to that in control group(aphids were fed with wheat leaves grown under natural light).(2) The effects of wheat exposed under UV-B radiation on the feeding behavior of S.avenaeCompared with the control group, the number of np waveform increased and the durationtime of C waveform prolonged significantly in the high intensity UV-B radiation group. Itindicated that the difficult of feeding behavior for S. avenae had been added and the effectivefeeding time had decreased. But the significant difference of those was not found in lowintensity UV-B radiation group. While the differences between the control group and the lowintensity UV-B radiation group were not significant. However, the time for the firstoccurrence of pd waveform was delayed in the two UV-B treatment groups. 2. The direct influence of UV-B radiation on the S. avenae(1) The influence of UV-B radiation on ecological parameters of S. avenae in differentgenerationsThe intrinsic rate of increase of S. avenae population exposed under UV-B radiationdeclined and then ascended with the increase of generations. And the infinite rate of increasefor S. avenae has the similar trend. While the birth rate of S. avenae population almostremained stable firstly and then climbed in the following generations. However, thedifferences of the mean length of a generation were not significant among generations.(2) The effects of UV-B radiation on the ecological parameters of S. avenae in the samegenerationIn the second generation, compared with the control group, the intrinsic rate of increase,the infinite rate of increase and birth rate of S. avenae exposed under low intensity of UV-Bradiation has no significant differences, while the result is opposite in the high intensity ofUV-B radiation group. And the result in the twelfth generation was totally adverse. Then inthe following nineteenth and twenty-sixth generations, there is no significant difference whencompared with the control.The mean length of a generation (T) of S. avenae population has no significant differencebetween UV-B radiation treatment groups and the control group in the second generation.However, the T of S. avenae exposed under low intensity of UV-B radiation was significantlyprolonged compared with the control in the twelfth and nineteenth generations. Then in thefollowing generations, such as the twenty-sixth generation, the difference between UV-Btreatment and the control was not significant.Compare with the control group, the significant difference of life table parameters of S.avenae exposed under high intensity of UV-B radiation turned up earlier than the S. avenaeexposed under low intensity of UV-B radiation. And the differences among three groups werenot significant after the nineteenth generation.In conclusion, UV-B could affect the ecological parameters of S. avenae indirectly anddirectly. And the high intensity of UV-B radiation could undermine the growth anddevelopment of aphids. But S. avenae may be adaptive to a long term UV-B radiation to someextent. However, study of the adaptive mechanism and the combined effects of indirect anddirect influence of UV-B radiation on the S. avenae are still needed.