Effect of various cauliflower cultivars on population density fluctuations of the cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its parasitoid Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

In this study, population density changes of the cabbage aphid, Brevicoryne brassica (L.), were tested in the field during 2011 under natural infestation at research field of the Shahed University (South of Tehran). This investigation was conducted on the eight cauliflower cultivars including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita in randomised complete block design with five replications. Sampling was done after starting of aphid activity in the field every week and the total number of adult aphids and nymphs were counted in three leaves of the upper, middle and lower parts of the plant. In addition, the percentage of parasitism of the cabbage aphid by Diaeretiella rapae was evaluated. Results of the sampling showed that peak of the aphid population were at the first half of November. The parasitism percent of the cabbage aphid by D. rapae was significantly different among studied cultivars (p?<?0.05). Therefore, it can be concluded that using of Smilla, Buris and SG cultivars probably increases the efficiency of D. rapae in the control of the B. brassica (L.).