88 Asian J Agri & Biol. 2017;5(2):88-98. Asian J Agri & Biol. 2017;5(2):88-98. Comparative Toxicity of Insecticides against Two Important Insect Pests of Cauliflower Crop Muhammad Imran 1* , Kanwal Hanif 2 , Munir Ahmad 2 , Muhammad Nasir 2 , Umer Ayyaz Aslam Sheikh 1 1 Department of Entomology, Faculty of Agriculture, The University of Poonch, Rawalakot, AJ&K, Pakistan. 2 Department of Entomology, Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan. Abstract Study was conducted to test four insecticides, profenofos, emamectin benzoate, λ-cyhalothrin and lufenuron against two field populations of Plutella xylostella and Spodoptera litura at different larval instars during 2010-11. The field populations collected from Rawalpindi and Taxila cauliflower fields was tested using leaf dip bioassay method under laboratory conditions. Results showed that emamectin benzoate was the most toxic insecticide for both P. xylostella and S. litura. However, profenofos was the second most toxic insecticides to different larval instars of S. litura and λ-cyhalothrin to P. xylostella. High LC50 values for lufenuron for this limited time exposure might be due to its slow acting as chitin synthesis inhibitor. Emamectin benzoate can be suggested as the most effective insecticides against both field populations along with profenofos and λ- cyhalothrin. Keywords: Spodoptera litura, Plutella xylostella, comparative toxicity, mode of action, age-dependent Introduction Cruciferous family especially cabbages and cauliflowers are the most important winter vegetables grown extensively in temperate and tropical areas of the world (Liu et al., 2003). Two lepidopteran insects, Diamondback moth diamondback moth (DBM) (Plutella xylostella L.) and tobacco caterpillar (Spodoptera litura Fab.) are the most destructive insect pest of cruciferous plants mostly for cabbage and cauliflower over the world (Shankar et al., 1996; MalliKarjuna et al., 2004). They feed mainly on leaves resulting in reduced superiority and quantity of food. Its serious attack can cause 30-100% crop failure if no insecticide is used for its management (Verkerk and Wright, 1996). Frequently usage of insecticides for long period, they have developed resistance against many insecticides which make it prominent insect pest in one of the 20 resistant insect species (Shelton et al., 2000; Mota-Sanchez et al., 2002). Variation in detoxification enzymes activity among S. litura strains could be attributed due to insecticide usage pattern (Karuppaiah et al., 2017). Selection of insecticide for the management of diamondback moth (DBM) and tobacco caterpillar required continuous testing under both field and laboratory condition, so it is important to select appropriate insecticide according to insect pest. Many insecticides having longer residual action on plants or insects like prothiophos, cartap and fenvalerate mixture are suitable for their management (Nakagome and Kato, 1981). Organophosphates have been considered as the most important group of insecticide due to variations in chemical structures (Liu et al., 2003). In Pakistan farmers relay only on insecticides to control insect pests and due to indiscriminate use of Received: May 02, 2017 Accepted: June 06, 2017 Published: June 20, 2017 *Corresponding author email: muhammadimran@upr.edu.pk Original Research Article AJAB