Population dynamics of wheat aphids and natural enemies in different wheat varieties.

The population of wheat aphids ( Rhopalosiphum padi Linnaeus, Macrosiphum avenae Fabricius) was affected greatly by the resistance in wheat varieties. The amount of wheat ophids per 100 wheat plants decreased with increasing of the resistance of wheat varieties. Responses of two aphid species to the same wheat varieties such as Minxian 169 were significantly different. The aphids of M. avenae per 100 wheat plants (630 aphids per 100 wheat plants) were 5 5 times that of R. padi (115 aphids per 100 wheat plants) at the peak stage of wheat aphids. On the other hand, the populations of natural enemies were not affected by the resistant varieties. Results suggested that resistance of wheat varieties and natural enemies could play an important role in controlling wheat aphids under economic threshold in the mid later stage of wheat development.