Characterization of Isoproturon Resistant Phalaris minor Biotypes Exposed to Alternate Herbicides under Cropped and Uncropped Situations

Field experiments were conducted at the Research Farm, Department of Agronomy, PAU, Ludhiana (Punjab) during 1998–99 and 1999–2000 to find out the efficacy of alternate herbicides to control isoproturon resistant biotypes of Phalaris minor collected from various districts of Punjab. Twenty-five biotypes were raised alone and alongwith wheat crop. Application of clodinafop 60 g ha⁻¹, fenoxaprop-p-ethyl 100 g ha⁻¹ and tralkoxydim 0.35 kg ha⁻¹ during 1998–99 and clodinafop 60 g ha⁻¹ and sulfosulfuron 25 g ha⁻¹ during 1999–2000 season provided complete control of all biotypes of P. minor. However, application of isoproturon at double the recommended dose i. e. 1.88 kg ha_-1 failed to kill P. minor. Of the 25 biotypes, one biotype was classified as sensitive and 17 as resistant types under alone P. minor growing conditions. When P. minor was grown with wheat during 1998–99, biotypes found to be sensitive, partially resistant and resistant were nine, nine and seven, respectively, while during 1999–2000, the number of biotypes under three categories was 7, 8 and 10, respectively. Dry matter production by P. minor was 2–3 times more while growing alone as compared to under cropped conditions.