Studies On Ecology Of Population Of Water Chestnut Beetle, Galerucella Birmanica Jacoby

Water chestnut(Trapa sp.) is one kind of important invasive plants in North Amercia. Based on the fisrt step study in Biology and Ecology, long term observation on water chestnut natural enemy, Galerucella birmanica Jacoby, the purpose of this dissertation is to probe into whether water chestnut beetle can become a natural enemy in North Amercia.At the same time it lay a foundation to develop control approaches against water chestnut beetle in China.The longevity of the water chestnut beetle adult was between 4 and 80days with average of 104 days. Female laid 10-318 eggs in its whole life. The larvae completed their growth in 9～12 days. Pupae required 3～4 days for development. Seven generations occurred with strong overlapping during one year in Yangzhou. First step host range tests with 5 plant species showed water chestnut is the best food of the beetle.The influence of temperature on the development, survival,fecundity etc of water chestnut beetle at 16℃,19℃,22℃,25℃,28℃,31℃,34℃ and the life tables at these temperatures were also presented. The results showed that the maximal duration of the whole generation was observed at 19℃, which is 49.69 days. The shortest duration of the whole generation was at 34,which is 18.09 days.The maximal duration of the Pupa is at 19℃ and the shortest is at 34℃.The temperature is higher, The duration of the whole generation is shorter. The highest death rate was mostly at 3rd instar or before. Oviposition period is maximum at 22℃,which is 15.6 days and shortest at 34℃,which is 8.6 days.The thermal sum were 346.8414 day-degrees.The relationship between temperature (T) and the rate of the egg development could be modeled with the equation:y=-0.873x2+49.669x-565.71 y—Average number of Eggs laid,x—TemperatureThe relationship between temperature (T) and the average oviposition period could be modeled with the equation: y=-0.5767x+27.347 y—Average oviposition period,x—TemperatureThe relationship between temperature (T) and the innate capacity of increase ould be modeled with the equation: Y=-0.0003x2+0.0231x-0.2756 y—innate capacity of increase, x—Temperature.The over-wintering imago had different cold-hardness at different time. winter hardiness is stronger as the temperature is lower. The super-cooling point (SCP) reach the lowest in middle winter.During one year,the maximum the number of water chestnut beetle population reach the highest point in beginning of June and bottom of setemper.,which is accord to the local climate.The water chestnut beetle population have some kind of self-adjust capacity.One couple of beetle can eat up 7 water chestnut during less than 2 moths.The effect of controlling water chestnut is remarkable. The density of beetle is bigger,the effect is more remarkable.