Effects of two potential pest management components, time of sowing and selective use of chemicals for the management of aphids (Lipaphis erysimi Kalt) in canola crop

A field study was conducted to evaluate seasonal aphid population and efficacy of different insecticides, Nuvacron 40 SCW (Monocrotophos), Edmethyl 50EC (methyl Parathion), Tamaran 500 SL (Methamedophos), Laser 25 EC (Cypermethrin + Dimethoate), Confidor SL 20 (Imidacloprid) against aphids (Lipaphis erysimi kalt) in canola crop. Two experiments, laid out in Randomized Complete Block Design (RCBD) with three replications, were conducted at Agricultural Research Institute, Tarnab, Peshawar during 2002-03. In the first experiment, the canola cultivar, Bulbu1098 was sown on 7-different sowing dates. The aphid infestation per plant was highest i.e. 216.10 aphids per plant on (2nd November, 2002, sowing date), while the lowest infestation i.e. 91.01 aphids per plant was recorded on (3rd September 2002, sowing date). The early sown crop with lowest aphid population provided highest yield of 2001 kg per ha, while the late sown crop with highest infest ation showed lowest yield of 605 kg per ha. In the second experiment, five insecticides were sprayed two times with an interval of 25 days against L. erysimi canola aphids sown on a separate plot. The minimum infestation per leaf was recorded in the range of 1.05-2.42, where Nuvacron was prayed. The maximum infestation among the treated plots was observed on Confidor treated plot i.e. in range of 4.19-5.43 but Overall, all treated plots showed lesser infestation as compared to the untreated pots i.e. in the range of 6.57-23.83 aphids per leaf after both sprays. All insecticides after 1-day followed by 3-days showed good control and their effectiveness decreased on 10th and 15th day's interval but still better than the untreated (check).