| The pine armored scale of Hemiberlesia pitysophila Takagi had been considered as a serious and alien quarantine insect pest for its great damages to various evergreen pines and rapid spread ability in Guandong and Fujian provinces of China since 1982. Through a series of field and lab experiments, this paper demonstrates the scale's occurrence, geographic distribution, diffusive ways and relationships with the pine forest environment, effectve forest management practices, chemical and biological control technologies. Based above research, the potential distribution regions are predicted, and relevant risk analysis is conducted combined with relative literatures in recent 20 years. The main results are as follows:1. The developmental threshold temperatures in the pine armored scale was measured with the mean value of 10.47±1.03℃, and 810.8735 day-degrees were needed to complete one generation. The generation number of the scale in Fujian Province were evaluated using the method of effective cumulative temperatures principle,. The results were proved to be consistent with the facts from field observations, so it provided a scientific basis for the forecast and control of this insect pest.2. One year field investigation revealed that the pest population was higher during January to June than during July to December. The population quantity kept high in the duration from mid-March to late June, and fell from early July to early October, and then gradually increased from late October to late December, in which the low instar nymph number played an important role. However, the mortality of the population showed an opposite trend against the population quantity. Moderate negative correlation were observed between the total number of population and the mortality of low instars nymph number, the monthly mean temperature, the highest monthly temperature and the highest monthly extreme maximum temperature. Whereas, significant positive correlations were showed between the population mortality and the monthly mean temperature, the monthly mean minimum temperature, the extreme minimum temperatures, and the extreme maximum temperature, especially, an extremely significant correlation with monthly mean maximum temperature was also found. So the above results suggested that the air temperature was an important meteorological factor to affect the pest population dynamic, and the high temperature could make against the development of the population.3. Contrastive experiments indicated that the population quantity showed significant differences between the host pine of masson pine, Japanese black pine and slash pine, in which the population quantity was the highest on Japanese black pine followed by masson pine, and slash pine was minimum. In laboratory conditions, mortality of the pest population increased with rainfall, and the mortality was significantly higher in nymphae than in adults, and especially for the nymph before sex differentiation. The population dynamic exhibited some differences between in sunny slope and shady slope. In the second half year, the peak time of the pest population seemed to appear earlier in shady slope than in sunny slope, but to appear later in the first half of year. Significant differences in population quantity between different forest canopy densities, and more scales were found in the forest with high canopy density. In addition, the pest population remained higher in windward slope than in leeward slope. The significantly different population number was also proved between the masson pine with different diameter. However, no significant differences of the population number were observed among different slopes, different pine associations and different forest ages.4. Using the methods of Berryman (1968) and Exclusion Index of Population Control (EIPC), the life table of the pine armored scale population was constructed. Results showed that natural death was the key factor affecting the natural populations, and the 1 st instar nymph was the key of death stage. The EIPC seemed to be the highest for the unknown factors followed by the predation mortality factor. The parasitoids and pathogens factors shared a similar EIPC with lower values, so their control efficiency against the scale could be not remarkable in the field. The population trend index I was 4.12,, and the population showed a increasing trend and its survival curve belonged to Price (1975) of A-type.5. Based on the pest's biology, ecology and the distribution of host pines, the potential distribution regions and their risk degree in China were analyzed and predicted using the geographic information system to develop quarantine measures.It was firstly defined as the potential high risk areas for occurrence of the pine armored scale including Taiwan, Guangdong, Macao, Hong Kong, most of Guangxi and Fujian, the southern of Yunnan and Hunan, Jiangxi. And the potential moderate risk areas covered north central of Hainan and Yunnan, northern of Hunan and Jiangxi, northeast and north-west of Fujian,Zhejiang, Jiangsu, Anhui, Hubei, Chongqing, Guizhou, Henan, Shandong and central and southern of Hebei, southeastern of Sichuan, south central of Shaanxi and Shanxi. And the low-risk areas southern were Tibet, northwest of Yunnan, southwest of Sichuan, southeast of Gansu, north of Ningxia and Shaanxi, west of Hebei and southwest of Liaoning. The potential distribution area for the scale possessed 41.5%of the total land area and more than 90%of the pine distribution area in China. The proportion to the total land in China of high, medium and low risk areas for the pest occurrence were 18.9%,58.7%and 22.4%, respectively.The results not only enriches the fitness of exotic forest pest and the theoretical basis of risk analysis, but also develop useful quarantine control strategies, monitoring and forecast measures for Hemiberlesia pitysophila Takagi in China.6. Qualitative and quantitative analysis with Pest Risk Analysis (PRA) method were run to determine the degree of potential hazards of the pine armored scale in China. The selected indices included the native and abroad distribution of the scale, the potential damages, the economic importance of hosts, the possibility of colonization and spread, and the difficulty of risk management, etc. Evaluation result_R=2.162 showed that this pest scale is a high risk forest pest in China. Although it only occurs in partial areas of China, but has strong adaptability and many suitable host pines with a wide geographic range. So, it is necessary and important to keep the pest scale in the China's entry plant quarantine pest list and the national forestry plant quarantine pest list, and prevent the pest scale's large area of dispersal through man-made long-distance transmission by various plant quarantine methods.
|
PDF Full Text Request