The Comparison of Infestation Rate of 21 Canola Genotypes to Cabbage Aphid (Brevicoryne brassicae L.) under Field Conditions in Uromia region

Cabbage aphid (Brevicoryne brassicae L.) is a important pest of canola (Brassica napus L.) throughout the world, and as the host plant resistance is considered as a useful method to control the pest, therefore twenty one genotypes of canola were evaluated from the view point of their resistance to cabbage aphid infestation in a randomized complete block design with three replications and under natural infestation conditions in Urumia during 2007-8. To evaluate the infestation rate of the genotypes, an infestation index indicator of the percentage of infested plants, the number of aphids per centimeter of stem length and the average length of the infested stems was used. The infestation to the aphid began in the mid May and continued till canola harvest time in mid-late June. In the last sampling synchronized to the maturity of canola seeds, the level of infestation was reduced. The different sampling dates indicated significant differences in the levels of infestation to aphid. Also from the stand point of the level of cabbage aphid infestation, canola genotypes were classified in four groups of resistant (including Sahara, Opera, Arc-2, Sintara, okapi and Sunday), semi-resistant (including SLM046, Modena, Milena, Arg-91004 and Regent Cobra), semi-sensitive (including Arc-5, Orient, Elite, Dexter and Licord), and sensitive (including Geronimo, Olpro, Ebonite, Talent and Celisius).