author(s)
Imtiaz Ali Khan, Mansoor Ahmad, Rasheed Akbar, Sajjad Hussain, Muhammad Saeed, Abid Farid, Ruidar Ali Shah, Walija Fayaz, Bismillah Shah, Mir Manzar Ud Din

abstract
A study on losses due to Brevicoryne brassicae in 12 Brassica genotypes under screen house conditions was conducted under screen house conditions during 2006-08. For the experiments artificialrninfestation of 5, 10 and 15 aphids/plant at flower-bud initiation stage was done in all the 12 genotypes. The results of the experiment of 5 aphids/plant infestation revealed that aphid density was significantly higher (106.2 aphidrnplant^-1) on Rainbow and lower (27.67 aphid plant^-1) on Raya Anmol and Peela Raya (30.17 aphid plant^-1). In the experiment of 10 aphids plant^-1 infestation, mean density of aphid was significantly higher on Legend (125.7 aphids plant^-1) and Westar (117.0 aphids plant^-1) while lower on Raya Anmol (57.67 aphids plant^-1) and T-16-401 (54.50 aphids plant^-1). In the experiment of 15 aphids aphids plant^-1, mean aphid density was significantly higher (200.70 aphids plant^-1) on Rainbow and lower (82.83 aphids plant^-1)rnon Ganyou-5. In control (0 aphids aphids plant^-1), Raya Anmol yielded significantly higher (7.32, 7.33 and 7.33 g plant-1) and Oscar lower (3.62, 3.62 and 3.60 g plant-1) in the 5, 10 and 15 aphids plant-1, respectively. Among the 5, 10 and 15 aphid infested plants, Ganyou-5 (4.98, 4.57, 3.45 g plant-1) yielded significantly higher and while Oscar (2.55, 1.60, 1.22) lower, respectively. The percent yield losses were significantly higher in Crusher (43.83%) and Torch (44.50%) and lower (11.08%) in T-16-401 in 5 aphid infested plant; significantly higher (62.15%) in Vanguard and lower in Legend (23.65%) and T-16-401 (22.09%) in 10 aphid/plant, and significantlyrnhigher (75.88%) in Vanguard and lower (29.14%) in T-16-401. The present results might be helpful in using host plant resistance in an integrated pest management program against B. brassicae on Brassica genotypes.