Interaction effect of water temperature for spraying clodinafop formulations on Phalaris minor biotypes

Pot studies were carried out at CCS Haryana Agricultural University, Hisar during 2006–07 and 2007–08 to evaluate the effect of water temperature for spraying clodinafop-propargyl formulations on several biotypes of P. minor and response to alternate herbicides. Clodinafop formulations (Topik, Point, Rakshak Plus, Moolah and Jai-Vijay) at 60 g/ha were sprayed using water at temperatures of 8, 25 and 40°C on P. minor biotypes J-35, KUL, F-42, B-6, H-2, Bajekan during 2006–07 and Garhi Birbal, Jyotisar, Sarwan, Nangla, Jat and Lalodha during 2007–08. Isoproturon 1.5 kg/ha, chlorotoluron 1.0 kg/ha, premix of sulfosulfuron+metsulfuron (Total) 32 g/ha, mesosulfuron+iodosulfuron (Atlantis) 14.4 g/ha, pinoxaden 45 g/ha, fenoxaprop-P-ethyl 100 g/ha and quizalofop-P-ethyl 100 g/ha were sprayed using normal water temperature (25°C) on P. minor biotypes. Chlorotoluron was replaced with clodinafop 90 g during the second year. Mortality of P. minor biotypes was significantly decreased with clodinafop formulations when water temperature of 8°C was used for spraying compared to 25 or 40°C temperature water. There was no difference in mortality of P. minor biotypes between 25 and 40°C temperature water for spraying, eight weeks after treatment (WAT); however, significant differences in dry matter accumulation by P. minor biotypes were recorded due to water temperature for spraying clodinafop. Clodinafop formulation, Topik was more effective compared to Jai-Vijay, but differences were non-significant among different formulations. Significant variations in mortality and dry weight were observed among P. minor biotypes with different herbicides. Chlorotoluron provided effective control of isoproturon resistant biotypes, which were also susceptible to quizalofop. Lalodha biotype was highly resistant to fenoxaprop, isoproturon and clodinafop and even increased rate of 90 g/ha clodinafop also failed to effectively control this biotype. Pinoxaden, sulfosulfuron+metsulfuron, mesosulfuron+iodosulfuron and quizalofop; however, provided 90–100% control of these resistant biotypes. Variations in mortality by pinoxaden, sulfosulfuron+metsulfuron and mesosulfuron+iodosulfuron herbicides were also observed in some biotypes which need further confirmation.