Population dynamics of cabbage aphid, Brevicoryne brassicae and identification of its natural enemies in canola farms in the North of Fars province

According to this research the population dynamics of cabbage aphid and identification the natural enemies in canola farms in the north of the Fars province that have been done during the years 2009 – 2010. Three species of aphids have been known; Myzus persica Sulzer, Brevicoryne brassicae (L.) and Aphis gossypii Glover. The cabbage aphid was the dominate species with 75.5% abundance. M. persicae and A. gossypii with 16.5% and 8% relative abundance in order were in the second ranges. Also in order to consider the population dynamics of cabbage aphid in the selected farms with 2 hectare spaces for each, gathering 30 leaves regularly by random from canola bushes weekly. So on the basis of these samplings it has been considered that the aphid population began at the middle of March until the middle of May at the time of blossom and sheathes was at the highest point, with the average temperature 7.5ºC daily and 77% R.H. Also regarding the natural enemies, 13 species of predatory and 1 species of parasitoid in the Coccinelledae, Syrphidae, Chrysopidae and Braconidae families have been gathered. This study revealed that in the canola farms the peak of natural enemies density occurred after the aphid's population peak of the late growing season. The most abundant predators were as follow: Coccinella septempunctata (L.), Scaeva albomaculata (Macquart 1842) and Chrysoperla carnea (Stephens 1836). Also a species of parasitoid Diaeretiella rapae (MIntosh 1855) has been found.