Effects Of Temperature And Pesticide On Parasitoid Aphidius Gifuensisand Identification Of Symbiotic Bacteria In This Parasitoid

Aphidius gifuensis Ashmead is a dominant parasitoid of Myzus persicae (Sulzer), which plays an important role in biological control of M. persicae. We evaluated the influence of temperature and pesticide on A. gifuensis development and reproduction in order to understand the adaptability of A. gifuensis to temperature and evalute the safety of pesticides on A. gifuensis in tobacco. We also detected the species of symbiotic bacteria in A. gifuensis by PCR-RFLP method because the symbiotic bacteria would be useful to improve the artificial breeding efficiency of A. gifuensis.We evaluated the development of A. gifuensis at five constant temperatures (10,18, 25,28,30?) in laboratory. Result showed that temperature had a significant impact on the developmental duration of A. gifuensis. Under the condition of 25?, the duraiton from egg to adult emergence of A. gifuensis was the shortest which was ten to eleven days. Under the condition of 10?, the developmental period was prolonged to 38 days. Between 10? and 28?, the temperature had no significant effects on the fecundity and eclosion rate of A. gifuensis. When temperature was higher than 30?, A. gifuensis could not complete the developmental period. The sex ratio of A. gifuensis increased with the temperature, and at 25?, the sex ratio close to 2:1. The longevity of A. gifuensis decreased with temperature, when it exceeded 30?, longevity became less than 1 day. The optimum temperature was 25? for artificial breeding and releasing A. gifuensis in large scale.We used a scanning electron microscope to examine and photograph the morphological characteristics of the antenna and sensilla of A. gifuensis that emerged normally. We also compared the differences in the sensilla between female and male adults. We stored mature larvae of A. gifuensis at 4? for 7,14,21, and 28 days to observe the effect of cold storage on the external form of the antennae and sensilla. Result showed that the antennae of males and females had a similar morphology, and both had flagelliform antennae. The female and male antennae were divided into 17 and 19 subsegments, respectively. There were six types of antennal sensilla on the adult antenna, namely, trichodea, chaetica, placodea, Bohm's bristles, coeleoconica, and basiconica sensilla. Sensilla coeleoconica II was found on only the male antenna. There was no sexual difference in the number of sensilla. Abnormal placodea and coeleoconica were observed after the larvae were stored at 4? for 14,21, and 28 days, and this influenced the segmentation of the last two antennal subsegments. Therefore in the process of large-scale propagation and release of A. gifuensis we should shorten the storage time to ensure the population of A. gifuensis in field.In order to evaluate the safety of pesticides to A. gifuensis in tobacco fields, the impacts of eight conventional pesticides on A. gifuensis were studied in laboratory using the insecticide film and dipping method. The results showed that the imidacloprid, acetamiprid, thiamethoxam and matrine had evident toxic effects on survival of the wasp adults, and the eclosion rates of adults significantly decreased when they were exposed to the imidacloprid, thiamethoxam and acetamiprid insecticides. Wings deformity of wasp was caused by these three insecticides used on mummies. However, the emamectin benzoate, lambda-cyhalothrin, pymetrozine and ningnanmycin were relatively safe to wasp adults and mummies. After treatment with these three insecticides for 1h, the mortality of wasp adult was 0-5.56%, while the eclosion rates of adults exceeded 70%. These results will provide a basis guidance to select insecticides in the integrated management of M. persicae.We detected the species of symbiotic bacteria in A. gifuensis through PCR-RFLP. We collected parasitoids sample at eleven different regions in Guizhou province that all were A. gifuensis, therefor A. gifuensis was a dominant parasitoids of M. persicae in tobacco field. The detection of Wolbachia endosymbionts in A. gifuensis using PCR method to amplify the wsp gene showed that there were no Wolbachia in all the A. gifuensis samples from Guizhou. We detected two families of symbiotic bacteria which belonged to the Proteobacteria, and the two families were Moraxellaceae and Sphingomonadaceae. The other family of symbiotic bacteria was Staphylococcus belonging to the Firmicutes. Detecting the species of symbiotic bacteria in A. gifuensis has theoretical and practical significance to improve the artificial breeding efficiency of A. gifuensis and the potential of controlling the occurrence and damage of M. persicae.