Ecology, Risk Analysis And Monitoring Tactics Of Woolly Apple Aphid, Eriosoma Lanigerum (Hausmann)

Woolly apple aphid, Eriosoma lanigerum (Hausmann), is an important plant quarantine target all over the world. It seriously damages apple trees, causing significant economic loss in the apple growing areas. Currently plant quarantine plays a crucial role in the international agricultural trade because of the lift of non-tariff trade barriers, and the decision-making of plant quarantine must be based on pest risk analysis (PRA). In the international trade, China takes an advantage over other countries in apple exportation for its good quality and special flavors, but the exportation is often limited by the plant quarantine barrier arising from the quarantine pests, such as woolly apple aphid. In order to promote global apple trade and support domestic apple production, the invasive ecological characters of woolly apple aphid were investigated, and its risk was analyzed. The tactics of monitoring epidemic situation for the pest were carried out in southwestern Shandong Province.1. Seasonal abundance of woolly apple aphid was studied using the methods of counting aphid patches of the wingless aphids, trapping the alate aphids with yellow sticky board and binocular microscope examination of the mummy aphids in southwestern Shandong Province,and the dynamic of woolly apple aphid on the different parts of the apple trees was analyzed. The results showed that two peaks of the aphid appeared in the orchards, one from the middle or last ten-day of May to the first ten-day of July, and the other from the last ten-day of August to the middle of October. The alate aphids also had two peaks, one from the first ten-day of April to the first ten-day of June and the second from the first ten-day of September to the first ten-day of October. In the different periods of the growing season, the number of the aphid was variable in different parts of the trees. The survey showed that the aphids crowded on roots, trunks and boughes, and seldom on branches and flushes before July. But after the middle of July, the number of aphids was much more on the boughes, branches and flushes than on roots or trunks. Spatial patterns of woolly apple aphid on the flushes,branches,trunks and roots of apple trees belonged to aggregation distribution and a sampling meathod in apple orchards was determined.2. The developmental zeros of the 1st– 4th instar nymphs, whole nymphs, adult and one generation of the aphid were determined at 9.10℃, 10.60℃, 12.48℃, 10.78℃, 10.76℃, 10.82℃and 10.56℃, respectively. The effective accumulative temperatures of the 1st - 4th instar nymphs, whole nymphs, adult and one generation were 32.67, 33.39, 22.00, 35.34, 123.19, 25.92 and 150.05 day-degree, respectively. By using the law of effective accumulative temperature, it was esitimated that the aphid yearly occurred 14 to 17 generations in southwestern Shandong and 13 -16 generations in the Yantai area. The cold tolerance of woolly apple aphid was studied, the supercooling point of the overwintering stage was -19.67℃, showing that the 2nd instar nymph of the aphid could overwinter safely in southwestern Shandong.3. Investigation of current apple cultivars in orchards showed that the number of aphid patches on different varieties or different parts on the same variety significantly differed. By using wind tunnel and olfactometer, the selection of apple woolly aphid to the branches of the different varieties was determined, and the responses to various odors from different varieties also varied. The results showed that the selection of woolly apple aphid to various varieties differred significantly, the aphid tended to select and harm Fuji and Gala more than Golden Delious and Red Star.4. Spatial niches of woolly apple aphid, other major insect pests and the natural enemies on apple trees were studied, and the insect community structure of the apple orchards infested woolly apple aphid was investigated. Twenty-three species of natural enemies were found and the dominant species included Aphelinus mali Haldeman, Coccinella septempunctata Linnaeus, Adalia bipunctata (Linnaeus), and Chrysopa phyllochroma Waesmael etc. The community diversity of woolly apple aphid and its natural enemies was low, showing the unstable community was easy to be disturbed in southwestern Shandong. The results could lay the scientific basis for sustainablly controlling woolly apple aphid and conserving its natural enemies.5. Using the genetic algorithm for rule-set prediction modeling system (GARP), the potential geographic distributions of woolly apple aphid both in the world and in China were analyzed. It was predicted that the population of woolly apple aphid could be established in the major areas of North America, Europe and Eastern Asia,as well as a few countries and regions in south of South America, Oceania and Africa. In China, it could be established in whole areas of Jilin,Liaoning,Hebei,Shanxi (Jin),Shanxi (Shan), Beijing, Tianjin, Shandong, Henan, Anhui, Jiangsu, Hunan, Hubei, Jiangxi, Chongqing,Shanghai,Zhejiang,Fujian,Guangdong,Guangxi and Guizhou, almost whole areas of Ningxia, the most of Gansu, Sichuan, Yunnan,Neimenggu and Heilongjiang, as well as a few regions of Xinjiang, Qinghai, Tibet, Taiwan and Hainan.6. Based on the relevant ecological characters of woolly apple aphid and the rules of PRA of international standards for pest measurements (ISPM), the risk levels of woolly apple aphid were analyzed qualitatively on the six aspects, i.e. distribution, host plants, potential damaged degree, economical and ecological significance, disperse possibility and risk management difficulty in China. The risk assessment system for woolly apple aphid was proposed and the values of the indices were given by some experts. The quantitative synthetic index of the pest risk is 2.06, suggesting the aphid has reached the high level of risk. According to the risk analysis, the high, middle or low risk of E. lanigerum introduced to the different main apple growing areas of China was determined.7. Based on the results of PRA, the scientific scheme and measures for the pest management against the plant quarantine barriers and trade issue were proposed in order to reduce the risk to an acceptable level in international apple trade, and to protect the national apple production. The eradication measures of woolly apple aphid in the newly and rarely occurred areas and a tactic norm for integrated management of the aphid for the seriously occurred areas were proposed.8. According to the Guidelines of ISPM (No.06), the techniques for monitoring epidemic situation of woolly apple aphid were explored, which will help to find and manage the pest timely in the high risk areas, and to improve the monitoring methods for the pest.