none The population dynamics of alates and apterous of turnip aphid (TA) Lipaphis erysimi (Kalt.) together with the incidence of parasitism by Diaeretiella rapae (M'Intosh) on five host vegetable varieties in the field were evaluated. The results showed that the average populations of TA apterous on host vegetable varieties turnip, Chinese kale, leaf mustard, flowering cabbage and Chinese cabbage were 63.425, 10.041, 24.928, 23.323 and 114.308 aphids/plant, respectively. The `critical day' was used to estimate the date when TA population density on host vegetable varieties reaches its economic threshold. The relationship between TA apterous population (x) and mummy aphids parasitized by parasitoid D. rapae was significant, and the regression formula is y=0.1211+0.0143x (r=0.9739* *). Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Land and freshwater zones; Palaearctic region; China Diaeretiella rapae (Aphidiidae); Hemipteran hosts; Lipaphis erysimi; Parasite prevalence, plant host influences; Guangdong; Guangzhou; Prevalence in hemipteran hosts, plant influences Lipaphis erysimi (Aphidoidea); Hymenopteran parasites; Diaeretiella rapae; Parasite prevalence; Plant hosts; Brassica & Raphanus; Host effects on population dynamics & parasitism by Hymenoptera; Population dynamics; Plant host influences; Guangdong; Guangzhou; Plant host effects on population dynamics & parasitism by Hymenoptera