Abstract: In order to investigate the roles of polyamine metabolism in larvae of oriental fruit moth， Grapholita molesta， during diapause period at low temperature. The dynamic changes of polyamine content， such as putrescine （Put）， spermidine （Spd）， spermine （Spm）， and the activities of ornithine decarboxylase （ODC）， S\|adenosylmethionine decarboxylase （SAMDC） and polyamine oxidase （PAO） in diapause larvae were measured. The results showed that Put content slightly decreased in the early period of diapause， then rapidly increased. Spd content maintained high level during the whole diapause development. Spm content decreased in the early phase of diapause， then significantly increased and then decreased again. The activities of ODC， SAMDC and PAO increased significantly. During diapause period， polyamine metabolism was significantly affected by diapause intensity and temperature， and the polyamine accumulation could help to improve the cold resistance of diapause larvae at low temperature.

Key words: Grapholita molesta, diapause, low temperature, polyamine metabolism