Population Dynamics Of Bactrocera Dorsalis And Invasion Origin In Wuhan, Hubei Province

Bactrocera dorsalis (Hendel) is an important invasive pest which has been excluded from "National Agriculture list of plant quarantine pests" released by the Ministry of Agriculture in 2009. The population monitoring in Wuhan City, Yichang City, Xingshan County and Badong City suggested that Bactrocera dorsalis has caused serious damage to citrus fruit production industry and vegetable production in 2007. In order to get the knowledge of population dynamics and to reveal the potential invasion origin for Bactrocera dorsalis in Wuhan, serving as basis for future implementation of suppression, two consecutive years (2008-2009) of the population monitoring by field investigation and indoor rearing, analysis of meteorological factors on the occurrence of population dynamics, the volatiles preference for 3 fruit varieties Tangerine orange, Satsuma orange, Chinese honey and Navel orange by using of Y-type olfactometer and microsatellite DNA markers used to get the potential invasion origin in Wuhan were conducted. The main conclusions are as follows:1. Population dynamics of Bactrocera dorsalis in Wuhan, Hubei Province and an correlation analysis of the climate factorsThere were 4-5 generations for Bactrocera dorsalis per year in Wuhan and the main infestation period in citrus orchard was the 4th generation. Bactrocera dorsalis population was characterized as a single-peak fluctuation from July to December. The population density increased rapidly from September, peaking at late October, and then decreased gradually in November. The population peak coincided with the orange maturity period. There was a significant increase in Bactrocera dorsalis population in 2009 compared with that in 2008. The sequence of transfer among host plants before citrus maturity was described as pear-jujube-persimmon-citrus. Population dynamics of Bactrocera dorsalis was relative to environmental factors such as the mean lowest and highest temperature per month, rainfall per month, and the number of raining days per month. The mean lowest temperature per month affected the population dynamics of Bactrocera dorsalis in Wuhan by using path analyses. Also, the mean lowest temperature was screened as the first principal component based on principal component analysis and cumulative variance proportion was 63.30%. The results revealed that temperature and host plants were the key factors responsible for the occurrence of Bactrocera dorsalis in Wuhan, Hubei.2. Preference for volatiles from different citrus varieties fruit by Bactrocera dorsalis adultsVolatiles of three different citrus varieties Satsuma orange, Chinese honey and Navel orange functioned well in attracting the Bactrocera dorsalis. The preference order for the three fruit volatiles were as follows:Navel Orange> Satsuma orange> Chinese honey. The pupae weight differed significantly among those feeding on the different variety fruit and the pupae weight of oriental fruit flies feeding on Navel Orange was significantly higher than those feeding on Chinese honey. However, there were no significant difference in emergence rate and sex ratio of those tested flies.3. Overwintering of Bactrocera dorsalis in Wuhan, HubeiFrom 2008 to 2010, for two consecutive years of winter, we investigated whether B. dorsalis could overwinter with the stages of adults, larvae, pupae in Xianjian village of Wuhan, Hubei. The results showed that a small population of B. dorsalis pupae could go through cold winter and overwinter successfully in Xianjian village of Wuhan, Hubei.4. The invasion origin of Bactrocera dorsalis in Wuhan, HubeiDegree of variation of Bactrocera dorsalis in Hubei Province was 3.47% compared with those in Fujian Province, and 1.09% compared with Guangdong Province. The degree of variation difference was not significant among three areas. Therefore, it may inferred that Hubei, Fujian and Guangdong share the same invasion origin. Of the two groups divided by k value analysis, flies from the Hubei, Fujian and Guangdong belong to the first branch with the K value at 0.979、0.986 and 0.967 respectively. Therefore, it can inferred that the invasion origin of B. dorsalis in Wuhan could be Fujian or Guangdong. The genetic distance of flies between Hubei and Guangdong was 0.1206, which was the shortest one, and it was 0.2385 compared with Fujian Population. Also, there was a genetic distance of 0.0990 between Fujian population and Guangdong population. NJ dendrogram was obtained for seven different flies population based on Ds and there was a shortest distance between the branch of Hubei and Guangdong population. Therefore, it can be concluded that the invasion origin of B. dorsalis in Wuhan, Hubei was Guangdong or Fujian.