Abstract
Avenafatua L. (Wild oat) is one of the world's worst agricultural weeds and is an ever -increasing threat in wheat growing areas of Pakistan. The injudicious application of herbicides for the control of A. fatua has resulted in the evolution of herbicide resistance and made it the second most herbicide resistance weed in the world. Studies were conducted to test the resistance status of A. fatuato clodinafop--propargyl during winter 2018-19 after conducting a field survey for the collection of suspected A. fatuaseeds from various locations of Sargodha division of Punjab, Pakistan. For the resistance confirmation, dose-response assays were conducted under the laboratory and greenhouse conditions. Four doses of clodinafop -propargyl (0, 0.5X, 1X, and 2X) were applied at 3-4 leaf stages of A. fatua. Mortality percentage and dry biomass of different biotypes were recorded at three weeks after herbicide spray. Lethal dose to kill 50% of plants (LD50), and resistance index (RI) were recorded based on mortality percentage. Results revealed that three biotypes (AF-SS-4, AF-SS-5 and AF-KSB-1) were resistant to clodinafop-propargyl. The mortality percentage for the resistant biotypes was 53%, 59% and 83%, respectively even at 2X. Resistance index was in the range of 5 to 7. Confirmation of A. fatuaresistance to the selected herbicide was the second case for herbicide resistance in Pakistan. Further research is warranted to evaluate the spreading of herbicide-resistant A. fatua in other areas and to suggest alternate practices to control A. fatua.