Resistance to isoproturon in Phalaris minor Retz. in Punjab
U.S. Walia, L.S. Brar and B.K. Dhaliwal, Department of Agronomy, Punjab Agricultural University, Ludhiana 141 004, India.
Investigations were conducted during 1993-94 and 1994-95 to study the occurrence of resistance in Phalaris minor Retz. to isoproturon and to find out effective alternative herbicides to control the resistant biotypes. Seeds of different phalaris biotypes were collected from farmer's fields where poor or no control of this weed was noticed over the last three to four years with post-emergence application of isoproturon. Most of the biotypes were not controlled by isoproturon even at double the recommended dose (1.88 kg ha-1) although it showed phyto-toxic effects on the wheat crop. All the biotypes were controlled by the post-emergence application of tralkoxydim 0.35 kg ha-1 and diclofop-methyl 0.90 kg ha-1 applied at 2-3 leaf stage of phalaris. These studies clearly show that phalaris populations have developed resistance to isoproturon. All (resistant and susceptible) biotypes when grown in association with wheat suffered severe competition reflected in greatly reduced shoot biomass as compared to phalaris monoculture. This implies that crop can assert a large smothering effect on phalaris thus aiding in better weed control.
Plant Protection Quarterly (1997) 12 (3) 138-140.