Studies On The Mechanism Of Population Increase And Disaster Of White-Backed Planthopper, Sogatella Furcifera(Horvath)

White-backed planthopper (WBPH) has become one of the most important pests in recent 10 years. With Laboratory experiment and field survey, this paper studies on the influrence of climate factors, rice resistant varies, nutrition state of the host plant and the population density on the increase of the hopper population, and try to sort out the key factors which may cause disaster. The results is as follows. The results showed that the occurrence of WBPH was determined by the population base size. There were significant relationships bctwecn the immigration number of generation of IV (one) and the number of mainly damaged generation in rice field. The immigration time of WBPFI was close related to the plum rain date. The earlier the rain date was, the earlier the migration time. And the migration size were related signil1cax~1y to the duration and days af plum rain. But the relationships between the precipitation of plum rain and migration population size was not significant. The landing populations of immigrated WBPH along the coast, lack and the mountaii areas wue lffger than that along the flatlands and riverside rice fields. The population of WBPI-I was very sensitive to temperattre. The optimum temperature was 24-2fC, and the reproduction, swvival rate of nymph and short wing rate become low when the temperature was below 24C or above 28C. The effects of resistance in different variety on WBPII population were studied. It was showed that the habitat rate and reproduction on Shanyou 63 were higher than on Wuyujing rice. The number of climax date of WBPH hi field was also higher on Sbanyou 63. The extension of hybrid varieties was the key factors to population breakout. The field resistance of some new varieties of rice were analyzed at southern 46 jiangsu province. The results showed that the resistance was better in the varieties of Bayou 161 and 96-50. And the resistance was different during the different developments of rice. There was significant population dependent of density in WBPH population. The relationships between survival and density of nymph, reproduction and density of adult were negative. The differentiation of wing and migration or detain were affected by temperature, food quality and density of population.