Abstract:

This study selected late maturing wild peaches as the test material, used the fruit peeling method to investigate the damage rate, insect status, and activity of the Bactrocera dorsalis in the autumn and winter seasons in Shandong Province, combined with local temperature data, established a logistic regression curve. The relationship between temperature and larval mortality rate in the fruit was studied through correlation and gray correlation analysis. The overwintering status and survival status of the B. dorsalis were investigated using soil planing and net covering methods. The results showed that the damage rate of the B. dorsalis in Shandong region was gentle in the early stage and significantly increased in the later stage, exhibiting obvious linear characteristics. The number of 1^st and 2^nd instar larvae gradually decreased with the time, while the number of 3^rd instar larvae increased. After November 23^rd, the number of 1^st instar larvae reached 0, indicating that the oviposition behavior of adults had basically stopped. Death began on November 16^th, rapidly increased on November 23^rd, and reached 100% on December 7^th, indicating that the larvae were unable to overwinter within the fruit. The temperature indicators have reached a highly significant positive correlation level, while the mortality rate of larvae has reached a highly significant negative correlation level with each temperature, indicating that temperature has a significant impact on the mortality rate of B. dorsalis larvae. According to the logistic equation fitting analysis, it can be concluded that the time of larval death in the peach fruit of the B. dorsalis in Shandong Province is between November 9^th and November 17^th. This fitting calculation is consistent with the actual situation in the field. Calculating the grey correlation between the mortality rate of autumn and winter larvae and the simulated values of temperature indicators show that the highest temperature in the external environment during autumn and winter has the highest correlation with the mortality rate of larvae, followed by the average temperature, while the lowest temperature has the least impact. By studying the overwintering stage by stage and the annual evolution process of the B. dorsalis, it is believed that the B. dorsalis cannot overwinter in the field in Shandong region, and the local parasites are still invasive and migratory population, the focus of prevention and control should be on external invasion prevention.

Key words: Bactrocera dorsalis, overwinter, larvae, temperature, correlation analysis, linear fitting, grey correlation degree