Study On Adaptability Of Ophraella Communa Lesage (Coleoptera: Chrysomelidae) To Low Temperature

Ophraella communa Lesage (Coleoptera: Chrysomelidae) is an important and specific natural enemy against invasive weed, common ragweed (Ambrosia artemisiifolia). In order to understand physiological and biochemical mechanism of its cold hardiness, forecast the probability that it migrate to North China and confirm the achieved feasibility of cold hardiness by cold acclimation, the differences in the cold hardiness among geographic populations and among seasonal populations and the effect of cold acclimation on this leaf beetle were studied in this paper. The main results were as follows:1. Cold hardiness of adult O. communa from different geographical populationsSupercooling point (SCP), Freezing point (FP), rate of water content and glycerol content in adult O. communa from Fuzhou, Nanchang, Miluo, Wuchang and Nanjing were detected in the laboratory. The results indicated that the cold-hardiness of adult O. communa increased with the increasing latitude. Cold-hardiness of Fuzhou population (i.e. the lowest latitude) was the highest, and that of Nanjing population (i.e. the highest latitude) among five geographic populations. The results suggested that to some extent, cold hardiness of O. communa have an ecological plasticity, thus it has a potential to migrate to North China.2. Cold hardiness of adult O. communa in different seasonal populationsSCP, FP, rate of water content and glycerol content in adult O. communa in different seasons were detected in the laboratory. The results showed that Cold-hardiness of adult O. communa changed with the seasonal alteration. The highest cold hardiness of adult O. communa was noticed in October, the next was observed in June and the lowest occurred in July.3. Effect of rapid cold acclimation on O. communaBoth discriminating temperatures for male and female O. communa were -12℃. 2 hours after rapid cold acclimation at 2, 5 and 8℃, survival rate, longevity and fecundity of adult O. communa were significantly increased. The results suggested that cold-hardiness of O. communa was improved and the negative effect of adverse intense low temperature on longevity and fecundity of adult O. communa could be partially removed by rapid cold acclimation.4. Effect of long-term cold acclimation O. communa2, 4 and 8 days after long-term cold acclimation at 4~8℃, both the longevity and fecundity of adult O. communa were increased. 8 days after cold acclimation at 4℃, the longevity of adult was significantly longer than control (CK, 28℃), and the female’s fecundity was not statistically different between cold acclimation and CK. 8 days after cold acclimation at 4~8℃, glycerol contents in F1 adult O. communa were higher compared with CK. The results revealed that O. communa can obtain cold hardiness by long-term cold acclimation, and the optimum condition is regarded as 8- day-acclimation time at the low temperature of 4℃.