| Whitefly Bemisia tabaci (Gennadius)(Hemiptera:Aleyrodidae) is one of the major insect pests in tropical, subtropical, temperate regions and their adjacent areas, it has many biotypes. Since B. tabaci B-type invaded China in the late1990s, it has spread rapidly over many provinces in China, and it also has heavier infestation trend in future. Chemical control is usually less effective due to the special characteristics of B. tabaci, e.g. tiny body for easy to transfer between host crops, high reproductive capacity, covered with a powdery and waxy secretion, and insecticide resistance, it still constitutes a serious threat to the production of crops such as vegetables and flowers in the garden. However, the control of B. tabaci in crop fields mainly relies on the pesticide, which causes the resistance of B. tabaci with the excessively and continuously use of pesticides, and does much harmful to the environment. Therefore, the biological control of B. tabaci may be an attractive alternative management. Parasitic wasp is one of important biocontrol system substrate in ecological agriculture and forestry. Introducing natural enemies is one of the best strategies for the management of invasive insect pests. It may enrich the resource of local natural enemies, improve the local insect community structure, and is an economic, security, and sustained effective method for invasive pests. In this paper, with Encarsia formosa and Encarsia sophia as the research objects which are two important parasitoids of B. tabaci, I studied these two parasitic wasp, mainly focus on the following three aspects:1. The internal reason of E. formosa and E. sophia to parasitise or host-feeding: structural anatomy of the female reproductive system.2. Host discrimination ability of E. formosa and E. sophia was measured:parasitic strategy selection strategy.3. The influence of E. formosa puncture on the emergence rate of the host or E. formosa. The results and conclusions were given as follow:1. Both parasitoid females had two ovaries, and the number of E. formosa ovariole changed from6to10, E. sophia’s was6. The numbers of mature eggs each female at6h、12h、24h、48h post emergence were constant essentially. The length of eggs increased gradually at6-24h post emergence, and reached the maximum at24h, then decreased afterward.2. E. formosa and E. sophia could accept the host parasitized by other wasps. E. sophia discriminate the parasitized host immediataly after E. formosa parasitize, and choose more health host to reproduce, but E. formosa need more time(24h) to discriminate. The host detection efficiency of E. formosa is lower than E. sophia, while the time difference among successively parasitism of the two wasps did not effect the handle time health host and parasitized host by others.3. E. formosa penetrated the host with its ovipositor to detect the condition of a potential host, and may form some sting marks on the host cuticula, the marks had a certain impact on the growth and development of the host or E. formosa. We observed when the number of sting marks was≤2, both B. tabaci and E. formosa could emerge; but when sting marks became≥3, only E. formosa could emerge, and no B. tabaci emerged, the total emergence rate reduced and total mortality rose significantly; when sting marks’number was>4, emergence rate of E. formosa decreased and the total mortality rate rose to30.77%. |
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