Effect of planting date and rape seed cultivar on the population and damage of mustard aphid Lipaphis erysimi in Khuzestan province

An experiment was carried out in split plot design with 3 main plot (Planting dates of 11, 21 Nov. and 1 Dec.) and 4 sub plot (cultivars Hyola 401, Hyola 308, PF and Option) and 4 replications in Behbahan Agricultural Research Station during 2005-2007. The experiments were carried out in sprayed and non-sprayed parts. The infected stem length, contamination percentage and index, capsule number, seed number in capsule, 1000 seed weight and seed yield were measured in sprayed and non-sprayed parts and the means were compared with Duncan test. The results showed that the lowest contamination index (0.97 and 1) were observed in Hayol 401 in the first planting date in two years and highest of contamination index (6.26, 7.08, 6.39 and 4.14) were observed in the PF and Option cultivars in the third planting date in 2005 and 2006, respectively. The highest seed yield was observed in Hayol 401 (3726 Kg/hect.) in the first planting date in 2006 and the lowest seed yield was observed in PF and Option cultivars (1738 and 1855 Kg/hect., respectively) in the third planting date. The seed yield reduces evaluated about %12-20 in the first planting date and about %23-33 in the third planting date in all cultivars and non-sprayed parts. Therefore, using suitable planting date of 11 and 21 Nov. and Hyola 401, 308 cultivars, can prevent population pick and damage of aphids in the most sensitive growth stage of canola (flowering stage) and finally yield loss.