Pak. J. Weed Sci. Res. 16(4): 403-408, 2010. RESPONSE OF Emex australis TO DIFFERENT POST- EMERGENCE HERBICIDES IN WHEAT (Triticum aestivum) Muhammad Mansoor Javaid 1 , Asif Tanveer 1 , Rashid Ahmad 1 and Muhammad Yaseen 2 ABSTRACT A field experiment was conducted to study the effectiveness of different post-emergence herbicides against spiny emex, Emex australis at the University of Agriculture Faisalabad, Pakistan. Fluroxypur + MCPA at 750 mL ha -1 , carfentrazone-ethyl at 50 g ha -1 , amidosulfuron at 60 g ha - 1 ,bromoxynil + MCPA at 1250 mL ha -1 , triasulfuron at 40 g ha -1 , thiofensulfuron-methyl at 100 g ha -1 , tribenuron-methyl at 100 g ha -1 and control (no spray) were tested. Carfentrazone-ethyl, fluroxypur + MCPA and bromoxynil + MCPA provided better control (86%, 85% and 76%, respectively) of E. australis over weedy check. Carfentrazone gave the maximum reduction in weed biomass (77%). While bromoxynil + MCPA gave maximum number of fertile tillers (427 m -2 ), number of grains spike -1 (47), 1000 grain weight (33 g) and grain yield (3.39 t ha -1 ). Thus, for the management of spiny emex, E. australis, the post emergence application of bromoxynil + MCPA and carfentrazone ethyl at 1250 ml and 50 g ha -1 , respectively is recommended. Key words: Emex australis, spiny emex, post-emergence herbicides, wheat. INTRODUCTION Weed infestation is one of the major causes of low wheat yield in Pakistan that reduces its yield by 17-50% (Anonymous, 1998). The magnitude of the yield losses depends on weed species, weed infestation duration and weed density. A member of family Polygoneceae spiny emex, Emex australis, is an erect or diffuse, much branched and throughout glabrous green weed, which has become an important agricultural problem (Shivas and Sivasithamparam, 1994). Due to its high competitive ability and reproductive potential, it has become a serious threat in Pakistan. It is hard and deep root system broadleaf weed, difficult to control due to its re-sprouting ability. Chemical weed control is considered the most effective, time saving and economical way of controlling weeds. However, herbicide response 1 Department of Crop Physiology, University of Agriculture Faisalabad. 2 Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Pakistan. E-mail: mmansoorjavaid@gmail.com