Population characteristics of Laodelphax striatellus and the relationship with temperature.

Abstract：Dioryctria rubella Hampson caused severe damage to Pinus kesiya var. langbianensis Chev. in Pu’ er city，Yunnan province has 3 generations a year and overlap extensively according to the field and laboratory observations of its biology and ecology. Its larvae infest shoots of pines and have the habit of transferring shoots， branch，and plant which based on the climate and the development conditions of its host. In the rain season， the damage rate is 35% － 40% via the action of tranferring plant. In the dry season，the damage rate is 90% － 100% via the action of transferring shoots. The third generation of D. rubella can cause more damage than the first and second one. The research results can facilitate the management of D. rubella.The population structure and dynamics of the small brown plant hopper ( SBPH) ，Laodelphax striatellus ( Fallén ) ， were investigated from 2007 to 2008 in Nanjing， and the relationship between the population size of SBPH and temperature was also analyzed. The results showed that there were two population peaks in spring and autumn，respectively，and two corresponding lower amounts in summer and winter. The lower population size in summer occurred in high temperature period. High-instar nymphae were dominant in the overwintering population of SBPH. The age-distribution of the summer population varied with years. Older nymphae were dominant in the summer population in 2007，whereas it was younger nymphae in 2008. The nymphae collected from rice fields developed normally in laboratory， and the amount of laying eggs was significantly increased after reared one generation. The summer population of SBPH did not diapause in Nanjing. The cold hardiness of SBPH was strong，and the super-cooling point of the 3 － 4th instar nymphae was below － 22℃ ，and there was no significant difference among reared temperatures or stages of overwintering.