Effects Of Elevated Temperature On Biological Control Of Bemisia Tabaci By Eretmocerus Hayati And Encarsia Sophia In Cotton Field

The tobacoo whitefly, Bemisia tabaci (Gennadius) MEAM1is one of the most destructive invasive insect pests in the world. While using chemical insecticide has caused a serious negative effects on ecology system, environmental satfty and human health, using biological control to manage whitefly is the most promising alternatives and has got a lot of progress. Global warming has caused great concern and affected the ecosystem and human beings. Under this circumstance, several questions have been brought forward. What is the consequence will be caused by global warming on B. tabaci? Will the effects of biological control of parasitoids be affected negatively global warming? To undertand the occurrence of B. tabaci, as well as the control effects of parasitoid under elevated temperature, in this thesis, we mainly focused on three contents:B. tabaci and parasitoids population dynamics, as well as the biocontrol efficacy of B. tabaci parasitoids under elevated temperature in cotton field; the synchrony changeged between B. tabaci and Eretmocerus hayati as well as the key responded life history traits under elevated temperature. The main research results are as follows:(1) A continuous survey of the population dynamic of B. tabaci and Er. hayati was conducted in open-top-chamber in cotton field in2012. Compared to the natural temperature control, the number of nymphs and adults of B. tabaci increased under elevated temperature, while the number of Er. hayati, the parasitism rate, as well as the synchrony between B. tabaci and Er. hayati decreased. Besides, the female sex ratio of offspring of Er. hayat increased under elevated temperature.(2) To better undertand why the synchrony between B. tabaci and Er. hayati decreased, we simulated the temperature dynamics in field experimental chambers in2012in climate chambers. Under the simulated environment, we found that the synchrony between B. tabaci and Er. hayati also decreased as in the field. The longevity, number of egg laying, emergence rate, as well as the developmental efficiency of Er. hayati were decreased significantly by elevated temperature, which might explain the why the symchrony decreased.(3) To better understand the biological control effects of single and combined release of parasitoids in elevated temperature, we evaluated the performance of two aphelinid parasitoids of B. tabaci, Er. hayati and Encarsia sophia, in open-top-chamber in cotton field in2013. The results showed that, compared to the natural temperature control, the population and parasitism rete of En. sophia were increased under elevated temperature, while that of Er. hayati decreased. This indicated that the high temperature caused benifical effects on the occurrence of En. sophia, while Er. hayati showed lower adaptability to high temperature. The cotton production was also reduced under elevated temperature, and the release of parasitoid improved the cotton production as compared to the no parasitoid released control. To achieve a good control effect, the relaseing combination should lean to Er. hayati under current climate, and lean to En. sophia in global warming environment in the future.