The Ecological Adaptability Of Different Geographic Populations And The Biological Characters Of Shandong Population In Colaphellus Bowringi Baly

The cabbage beetle, Colaphellus bowringi Baly (Coleptera: Chrysomelidae) is a serious pest of crucifers in China. Being material, this paper studied it's biological characters of Shandong population, the ecological adaptability of different geographic populations. The following aspects were concentrated: a) the influence of different photoperiod and temperature combinations on the diapause induction in different geographic populations of Colaphellus bowringi, b) cold hardiness and the survival ability of diapause and non-diapause adult of different geographic populations under low temperatures, c) the effect of photoperiod and temperature on overwintering adults'cold hardiness. Main results were summarized as follows:1. Effects of photoperiod and temperature on the diapause induction The duration of the night of 12~24h could hamper diapause effectively to Jiangxi population. When the duration of the night is shorter than 12h, it can induce diapause more or less. The 4~8h duration night induced a higher diapause rate clearly. There were no photoperiodic responses in Heilongjiang and Shandong population.The temperature cluld induce diapause alone. When the mean temperature was≦ 20℃, all individuals entered diapause. The incidence of diapause of three popualtions gradually declined with increasing mean temperatures. Under 28℃, the diapause rate of Jiangxi and Shandong population were 22% and 92% respectively, all individuals of Heilongjiang were still in diapause. When the temperature reached 30℃, the diapause rate of Jiangxi and Shandong population were 22% and 92%, the diapause rate of Heilongjiang population was 94%.2. The cold hardiness of Colaphellus bowringi Baly.The cold hardiness was strengthened with the increasing latitudes. The supercooling points of Heilongjiang, Shandong and Jiangxi population were the lowest in January, which were–23.7℃, -22.3℃and -20.7℃respectively. There were clear difference among three populations.The results showed that there was different between diapause and non-diapause adults in the same geographic population. Under–20℃, the 50% lethal time (LT50 ) of diapaused adult were 0.99h, 0.75h and 0.64h, which of non-diapause adult were 0.50h, 0.34h and 0.29h respectively. The cold hardiness of diapause adult was stronger clearly than non-diapause adult, northern population was stronger than southern. It showed the same results under other low temperatures.The supercooling points of adult were all lower than local mean minimum temperatures, can overwinter safely.Being cold acclimated with 4℃for 10 days, there was no change in cold hardiness of Heilongjiang population, different enhancement in Shandong and Jiangxi population. The supercooling points of three populations were not change after cold acclimation.3. The effects of photoperiod and temperature on cold hardiness The high temperature and short photoperiod could decline the supercooling ability. The long photoperiod could hamper this effect but could not reverse it. The effect of photoperiod gradually disappeared with the increasing latitudes. The temperature played a key role. Being treated 40 days with different photoperiod, there was no different in supercooling point of Heilongjiang population.4. The biological characters of Shandong population, Colaphellus bowringi Baly. There are four stages, egg, larvae, pupae and adult. It had two distinct infestation peaks in Shandong Province, one in spring and the other in autumn. The beetle aestivated and hibernated as adults in the soil. There was 1~2 generations per year. Some individuals take more than one year to complete one generation.The adults could mate many times during their reproductive period. Under 25℃, the egg-laying period of most females was 11~34 days, and the female could lay 861 eggs on average. The papae period was 3~5 days. Pupating were concentrated on 0:00~8:00 and occupied 66.3% of all. Emergence occurred during the day mainly.5. Effect of temperature on developmental and fecundity During 15~28℃, the development durations of different stages shorten with the increasing temperature. On 15℃, the durations of egg, larvae and pupae were 13.95, 23.45 and 12.37 days. On 28℃, they shorted to 5.03, 8.45 and 4.33 days respectively.The temperature affected the survival of every stage. The survival rates were high during 15~28℃, even reached 90% from 20~25℃. But it was low under 30℃, and the hatch rate of egg was only 48.17%.The longevity of post-diapause females significantly increased with decreasing temperature.