Comparative Resistance of Different Canola (Brassica napus L.) Varieties Against Turnip Aphid (Lipaphis erysimi Kalt.)

Resistance of different canola (Brassica napus L.) varieties against turnip aphid (Lipaphis erysimi Kalt.) was studied during 2002-2003 crop season at the University College of Agriculture, Multan, Pakistan. Ten varieties were planted on 16th October, 2002. Sampling for aphid was done at weekly intervals from last week of February to the last week of March, 2003. Population was recorded on 10 cm of inflorescence by gently beating it on white sheet and counting the falling aphids. Number of aphid was non-significantly different among varieties on different sampling dates. Seasonal mean population was significantly different on all the tested varieties. Maximum population (9.1 aphids) was recorded on the variety Con-I and minimum (4.0 aphids) was found on KS-75. Mean number of aphid on other varieties were 8.4 on Oscar, 7.6 on Rainbow, 5.9 on Con-II and Westar, 5.6 on Shiralee , 5.5 on Dunkeld, 5.4 on Con-III and 5.2 on Abaseen. Based on the mean seasonal population it is concluded that the variety KS-75 was resistant against turnip aphid. Varieties Westar, Abaseen, Con-I, Dunkeld and Shiralee were moderately resistance and Con-I, Oscar and Rainbow were susceptible.