Abstract: he study on the dynamics of soluble sugar and endogenous hormone contents in steppe grass species Elymus sibiricus,E.rectisetus,Leymus chinensis,L.racemosu and Stipa krylovii during their germination period in spring showed that high content GA and low content ABA played an important role for L.chinensis and L.racemosus germination,and the abundant soluble sugar storage in root made the rhizome grasses germinate earlier and grow stronger.The dynamics of ribosylzeatin was similar with that of soluble sugar in root,i.e.,declined in early germination period,reached the lowest by the end of April,and ascended then,while the IAA and GA contents had a similar variation trend with the soluble sugar content in bud,i.e.,all ascended gradually.There was a significant difference in the contents of GA,ABA and soluble sugar between rhizome grasses L.chinensis and L.racemosus and fibrous-root grasses E.sibiricus and E.rectisetus.

Key words: Cotton bollworm, Flight capacity, Migration, Facultative migration