Abstract: The relationships among the Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), other wheat aphids, natural enemies and abiotic factors were investigated in wheat, barley and oat fields in Xinjiang Uygur Autonomous Region, China, using theory of grey control system. The results indicated that competition of other wheat aphids with RWA and predation of natural enemies were the leading factors controlling the RWA population. Abiotic factors played secondary effect, among which precipitation and relative humidity in air were important relatively. The most important natural enemy of RWA was coccinellids in both wheat field in Tacheng and oat field in Ili. However, aphelinids and Leucopis spp. Were the most important enemies in wheat and barley fields in Ili respectively.

Key words: Russian wheat aphid (Diuraphis noxia (Mordvilko)), natural enemies, abiotic factor, grey control system