Population Ecology Of Water Chestnut Beetle,Gallerucella Birmanica Jacoby

The water chestnut beetle, Galerucella birmanica Jacoby, is a destructive pest of water chestnut in China, India etc. . The purpose of this paper is to investigate the biology and ecology of Galerucella birmanica that may not only be useful for the control of this beetle in China, but also helpful for its potential introduction and release in North America. The main contents and conclusions are as follows:1. Hybrid experiment showed that G. niponensis that fed on Brasenia schreberi reported by Lin Meixin should be G. birmanica.2. The population of water chestnut beetle had two peaks at pre-summer and pre-autumn. The standing high temperature could lead to swiftly decline of population and the climate condition is the key factor to influence population dynamic. I analyzed the spatial distribution pattern by two regression models and nine indices of aggregation. The theory sampling number and the compound sequential sampling methods were presented on the base of the spatial distribution pattern.3. In Yangzhou area, there were 7 generations of the water chestnut beetle per year. The beetle overwinters in adult. Fed on Trapa natans, the mean development times of the beetle were as follows: eggs, 4.74 days; larvae, 8.59 days; pre-pupae, 1.52 days; pupae, 3.18 days; adult, 17.00 days, and the whole generation, 35.03 days at 28 C in lab.The influence of temperature on the development, survival and fecundity of water chestnut beetle at 16, 19, 22, 25, 28, 31, 34 C were presented. The results showed that the shortest duration of the whole generation was 28.06 days at 34 C, the highest survival rate was 65% at 31 C, and the maximal fecundity was observed at 28 C, at the same time, I simulated the trends of fecundity and the relationship between fecundity and temperature. By linear regression method and the optimum seeking method to analyze the thermal threshold and the thermal sum, the results showed that the former method was better than the latter, and the thermal threshold for eggs to adults were10.36, 9.88 C, and the thermal sum were 640.57 , 664.18 day-degrees, respectively. The adaptable temperature range for the development of the water chestnut beetle was between 19 C to 34 C. It was very difficult to hatch for eggs when the temperature was above 36 C, and no eggs could hatch when the temperature was above 38 C. The supper-cooling points of the pre-winter adults, mid-winter adults, and post-winter adults were -10.33 C, -18.63 C and -14.79 C respectively. There were different mortalities of G. birmanica at different low temperatures. The water chestnut beetle could survive over the winter outside in Yangzhou.4. The life tables and the reproductive characteristic life table of experimental population of water chestnut beetle were studied at different temperatures. The results showed: the population trend index raised first then declined with the increasing of temperature and reached the top at 28 C, the innate increase capacity (rm) was 0.1152. the finite increase rate ( ) was 1.1221 per day, the net reproductive rate (R0) was 34,5974 per generation, the mean generation time (t) was 6.0171 days. The results of stable age-distribution, instantaneous natality , instantaneous mortality of water chestnut beetle at different temperatures shovved: the percentage of the immature was quite high, more than 85%. The reflecting time shorten with the raise of temperature.5. The influence of temperature on the development, survival and fecundity of different water chestnut beetle populations collected from Liaoning, Shandong,Yuannan and Jiangsu Provinces at 19, 22, 25, 28, 31 C were presented. The results showed that temperature was the key factor that affected the developmental speed of water chestnut beetle. The developmental rate gradually quicken with the increasing of temperature from 22 and 31 C. The relationship between developmental rate and temperature accorded with logistic model. In the progress of development, the mortality of...