Pakistan J. Zool., vol. 44(4), pp. 991-995, 2012. Effect of Plant Spacing on Aphid Population, Yield Components and Oil Contents of Late Sown Canola, Brassica napus L. (Brassicaceae) Muhammad Razaq 1* , Sajid Maqsood 1 , Muhammad Aslam 2 , Sarfraz Ali Shad 1 and Muhammad Afzal 3 1 University College of Agriculture, Bahauddin Zakariya University, Multan-60800, Pakistan. 2 COMSATS Institute of Information Technology, Pir Murad,Vehari, Pakistan 3 University College of Agriculture, University of Sargodha, Sargodha, Pakistan. Abstract.- Cabbage aphid, Brevicoryne brassicae L. and mustard aphid, Lipaphis erysimi (Kalt.) are the common insect pests associated with oilseed rapes in the Pakistan. An experiment was conducted to determine the effect of plant spacing on populations of B. brassicae and L. erysimi, yield components and oil contents of late sown canola, Brassica napus L. The crop was sown at 10, 20 and 30 cm plant spacing in Randomized Complete Block Design in three replicates at experimental farm of the Bahauddin Zakariya University, Multan on December 26, 2009. The aphid densities were recorded weekly from the top 10 cm of the inflorescence by gently beating it six times on a white plastic sheet from start of aphid appearance untill the time of harvest. Populations of both aphid species were non-significantly different on plants in all three spacings of B. napus. Yield, plant height, numbers of pods per plant, pod length, number of racemes and oil contents were also non-significantly different among all the treatments. Keywords: Canola, cabbage aphid, mustard aphid, canola oil, Brassica napus, Brevicoryne brassicae, Lipaphis erysimi. INTRODUCTION The oilseed plants, belonging to family Brassicaceae, are economically important crops around the world. Importance of oilseed crops can be visualized from the fact that during the year 2008-09, the total production of edible oil met 27.2% requirements of Pakistan, whereas remaining amount was imported by expending 84 billion rupees (Anonymous, 2009). B. napus occupied a minor position among the oilseed crops in Pakistan. But it is more important from health point of view as its oil contains lower amount of saturated fats (5- 8%) than any other vegetable oil (Raymer, 2002). Oilseed rapes suffer heavy losses from attack of aphid species like Brevicoryne brassicae L. and Lipahis eyrsimi (Kalt.) throughout the world. L. eyrsimi causes 10-90% losses in India to these crops depending upon severity of damage and crop stage (Rana, 2005). Losses due to B. brassicae and L. eyrsimi reach to 70-80% in Pakistan on different oilseed rapes. In the years of sporadic attack and severe infestation there may be no grain formation __________________________ * Corresponding author: mrazaq_2000@yahoo.com , aslamuca@yahoo.com 0030-9923/2012/0004-0991 $ 8.00/0 Copyright 2012 Zoological Society of Pakistan at all (Rustamani et al., 1988; Khattak et al., 2002). Both aphids are the common insect pests of rapes in Southern Punjab, Pakistan. Late sown canola, B. napus suffered 75.06% losses during crop year 2008 at Multan in Southern Punjab. Such heavy losses are difficult to avoid without application of insecticide (Razaq et al., 2011a). Pest management practices, like host plant resistance and biological control and other than chemical control are environmental friendly (Speight et al., 2008). Research on different varieties of B. napus has proved that available varieties do not possess sufficient amount of resistance to avoid the damage by the aphids (Amer, et al., 2009; Razaq et al., 2011b). Natural enemies like Chrysoperla spp. and lady bird beetle, Coccinella septempunctata (L.) appear at the later stage of crop when most of the damage has been caused by aphids to brassicas in Multan. Moreover, populations of these two natural enemies are too low to reduce numbers of aphids (Aslam and Razaq, 2007). In many parts of the world the use of insecticides is the only option to reduce the damage from aphids to these crops (Brown et al., 1999; Bhowmik, 2003, Hainan et al., 2007). The cultural pest management involves changes in crop production practices to make the crop less suitable for the pest or to make it more