The Effect Of High Temperature On The Bradysia Odoriphaga Biological Character

Bradysia odoriphaga Yang et Zhang, belongs to Bradysia, Sciaridae, Diptera. It destroys many vegetables like Chinese chives, onion and etc. Because of the small body, widely distributed, generations overlap; it has severely harmed the quantity and quality of Chinese chives. Due to the field population was influenced obviously by seasonal fluctuation, generally in the summer when the dramatic decline in the number of species. In the autumn, the population has a large number of outbreaks. It is reported that temperature and humidity are the important factors influencing the occurrences of Bradysia odoriphaga Yang et Zhang. In our research, we study the biological characteristics of adults and larvae of Bradysia odoriphaga Yang et Zhang under high temperature, and design to clarify effects and the key factor of the Bradysia odoriphaga Yang et Zhang population dynamics, so as to guide the population prediction and propose effective method of control. The main results are as follows:(1) The adults of Bradysia odoriphaga Yang et Zhang were exposured to 33℃, 35℃, 37℃ for 30 min to 120 min, and discovered the survival rate. The results showed that the survival rate of both sexes were above 90% and 85% under the exposure temperature of 33℃ and 35℃, respectively. Furthermore, the survival rate of both sexes were declined with the increase of exposure time and the declined pace of females was faster than that of males. U nder the exposure temperature of 37℃, the survival rate of females significantly declined as the exposure time increased(declined to 40%), while the survival rate of males didn ’t significantly decline(declined to 70%).(2) We have studied the biological characteristics of the next generation of Bradysia odoriphaga Yang et Zhang after exposing to high temperature. We have found that the longevity of males was longer than females. And a little increase in temperature was helpful for increasing the longevity of the adults. Heat stress could affect the preoviposition of females, however didn’t affect the oviposition. The number of females’ oviposit eggs was related to exposure time inversely. Heat stress has an effect on mating ratio.(3) At the exposure of 37℃ for 90 min, females oviposited eggs, however, the eggs did not become larval.(4) As the increase of exposure temperature, the numbers of eggs that females produced were decreased. For example, the ratio of the eggs number which were more than 100 that females produced were reduced, while the ratio of the eggs number which were 0 that females produced were increased.(5) When the adults were exposed to high temperature, the results of heat stress had an important influence on the next generation, especially effects the development period of larval. When pupae turn out to be the adults, the ratio of females were significantly increased.In summary, the heat stress has an influence on the development of Bradysia odoriphaga Yang et Zhang and the next generation. Because the adults of Bradysia odoriphaga Yang et Zhang mainly activate on the surface of ground under natural condition, the adults inevitably face the short-term severe high temperature in summer. The adverse effect of intense heat in summer on Bradysia odoriphaga Yang et Zhang and the next generation is closely related to low quality of the pest. The outbreak quality of the pest is greatly influenced by high temperature in autumn, and the change of developmental period has the close relation with high temperature. So having knowledge of high temperature on Bradysia odoriphaga Yang et Zhang biology contributes to effective comprehensive control and provide a theoretical basis for scientific prevention and control measures.