Studies On The Occurrence Of And Control Technology Against Bactrocera Dorsalis In Wujiang District

The oriental fruit fly, Bactrocera dorsalis is a destructive quarantine pest in fruits and vegetables in Asian-Pacific region. It has spread northward gradually in recent years in China, and caused serious damage to citrus fruit in Southern parts of Jiangsu province (such as Wujiang and Suzhou). As an alien invasive species, the occurrence characteristics of Wujiang population might be different to others. Therefore, the occurrence of B. dorsalis in Wujiang city was investigated in laboratory and field conditions in this study. The main results showed as follows:According to field occurrence survey from2006to2010in Wujiang dictrict, the colonizing of B. dorsalis has been established in the region, and damaged seriously,which should be controlled by different methods.Results from occurrence survey showed that the occurrence of B. dorsalis in the region start in August, and reached the peak point in Septenmber and October. The lower temperature during the period from the end of the year to the beginning of the next year decreased the population and delayed the peak point of occurrence, such as in2008.By an artificial rearing method in laboratory, the effects of temperature on the development of B. dorsalis were studied. The results showed that development rates of B. dorsalis at each stage increased with temperature between17℃to33℃. By using linear regression model and direct optimal method, the development threshold temperature (DTT) was determined, which was9.9℃for the developmental period from egg to adult, and was10.5℃,9.6℃and10.3℃for the egg, larva and pupa stages, respectively. The effective accumulation temperature (EAT) was381.0day-degree for developmental period Although average air temperature and average temperature at5cm soil depth in March and April were above DTT, according to meteorological data, field trapping date showed that the first adult appeared in late May in each year. These results demonstrated that B. dorsalis could complete4-5generations each year in Southern parts of Jiangsu province represented by Wujiang city and probable diapauses in spring.Trap experiment showed that:the control effect of frequency vibration light was not satisfactory, which was less than50%. The trapping effect of methyl eugenol (16/667m2) is most significant, which reached82.76%, especially in later period.The result of field efficacy trials of different pesticide showed that the control effect of chlorpyrifos of35%EC (667ppm), cypermethrin of25g/L EC (400ppm) and imidacloprid10%WP (500ppm), varied from70%to90%, and these agents can be used in controlling B. dorsalis in citrus orchards.