Evaluation of Fenoxaprop-P-Ethyl Resistant Littleseed Canarygrass (Phalaris minor) in Pakistan

ABSTRACT To test resistance status of Phalaris minor (littleseed canary grass) to fenoxaprop-P-ethyl in Pakistan, a field survey was conducted during 2014. Uncontrolled P. minor plants were selected for seed collection from wheat fields where fenoxaprop-P-ethyl was used to control P. minor. Seeds were collected from eight different locations near Fasialabad, Pakistan. Susceptible plants were also selected near Faisalabad having no history of fenoxaprop-P-ethyluse for comparison. These seeds were grown in pots for resistance confirmation using completely randomized design with factorial arrangement having four replicates. Four doses of fenoxaprop-P-ethylcontrol (0X), 46.9 (0.5X), 93.7 (1X) and 187 (2X) g a.i. ha-1 were sprayed at 3 to 4 leaf stage of P. minor. Three weeks after fenoxaprop-P-ethyl spray, percent mortality and biomass of different biotypes were recorded. Dose killing 50% plants (LD50) and resistance index (RI) were calculated on the basis of percent mortality. Results revealed that out of eight biotypes (PM-FS-1, PM-FS-2, PM-FS-3, PM-FS-4, PM-FS-5, PM-FS-6, PM-FS-7 and PM-FS-8) four biotypes (PM-FS-1, PM-FS-2, PM-FS-6 and PM-FS-7) showed resistance to fenoxaprop-P-ethyl. Percent mortality for the resistant biotypes was 51 to 71% even at 2X. Resistance index of the resistant biotypes was 2.13-6.00. Biomass reductions were also significantly lesser in resistant biotypes. Evolution of P. minor resistance to fenoxaprop-P-ethyl is first case of herbicide resistance in Pakistan. Research is needed to assess the infestation of herbicide resistant P. minor area in other locations and suggest control measures to evolve the effective management strategy to control the future spread of resistant biotypes.