Comparison Of Biological Characteristics Of Laodelphax Striatellus On Different Geographical Populations

Laodelphax striatellus, the small brown planthopper (SBPH), distributes throughout China and seriously in the Yangtze River Basin and North China rice areas. SBPH has the characteristics of big intrinsic rate and high environmental adaptability. In recent years, due to the effects of global warming, fanning system and other factor changes, the large-scale outbreak often occurred. Due to difference of the environment, the climate and land habitats, SPBH population is likely to be with geographical differentiation, including differences in population structure, development and dynamic. About SPBH geographical populations, most studies were on the migration, mass poisoning and diapauses, but little on the biological characteristics. In the present study, the apparent differences, developmental duration, effective accumulated temperature and viability of different SPBH geographical populations (Shenyang, Jining, Zhengzhou, Nanjing and Jiaxing) were determined and compared. The main results were as following:In body length, sex ratio and wing type, there were some differences in different SBPH geographical populations. In both males and females, the body length of the populations from high latitude areas (Shenyang and Jining) was significantly bigger than that from low latitude areas (Zhengzhou, Nanjing and Jiaxing). The sex ratio analysis showed that the ratio was0.66for Shenyang population,1.42for Jiaxing population and close to1.00for other three populations, which revealed the big difference among areas. The quite low female ratio and high ratio of long-winged adults in Shenyang population might indicate that the local environment was not suitable for SBPH population development.There were some differences in the developmental duration in different geographical populations. With the increase of temperature between19and28℃, the developmental velocity increased in all populations. However, when temperature increased from28℃to31℃, the developmental periods became longer, especially in Shenyang, Jining and Zhengzhou populations. At all temperatures, the developmental velocity in Shenyang and Nanjing populations was close, and Jiaxing and Jining populations were close. The best temperature for the nymph development of Shenyang population was26.8℃and27.5℃ for other populations. The order of the maximum growth rate was Zhengzhou>Jiaxing>Nanjing>Jining> Shenyang.The developmental threshold temperature of different geographical populations of nymphal stages was similar and between11-12℃. The effective accumulated temperature of Shenyang and Jining populations was the largest. The minimum was in Zhengzhou population and close to that of Nanjing and Jiaxing populations. According to the values of effective accumulated temperature of each instar, Shenyang and Jining populations were recognized as the cluster1, and Nanjing and Jiaxing populations as the cluster2. The effective accumulated temperature in Zhengzhou population was close to that of Nanjing and Jiaxing populations and also was included into the cluster2. SBPH in the cluster1kept in the winter condition for a long time to avoid fast development and the effective accumulated temperature had a large value. Although Zhengzhou is a northern area, the inland warm climate broke the limit of low temperature and the effective accumulated temperature in Zhengzhou population was close to that of two south populations, Nanjing and Jiaxing.In viability, the nymph survival rate, the longevity of adults and fecundity were tested. The nymph survival rates in Jining and Zhengzhou populations were lower than other three populations. For the longevity of adults, Jining population had the lowest data at all tested temperatures. Shenyang and Nanjing populations showed some advantages in the fecundity. Although there were differences among populations in these tested data, the correlation between these differences and latitudes was not obvious.In conclusion, the possible differences among five SBPH geographical populations were compared from the apparent characteristics, developmental duration, effective accumulated temperature and viability aspects. The results provided important information on the geographical differentiation in SPBH and were useful for the macro forecast and effective control of SPBH.