Sensitivity of littleseed canary grass populations from Punjab, India, to clodinafop‐propargyl and isoproturon

Abstract

AbstractLittleseed canary grass (Phalaris minor Retz.) is one of the most prevalent and troublesome annual grass weed species in wheat across the Indo‐Gangetic plains (IGP) of India, including Punjab. Littleseed canary grass has evolved resistance to different herbicide sites of action in the IGP region. A targeted field survey was conducted in 2018 and 2019 for seed collection of littleseed canary grass populations (total 94) across different districts of Punjab state prior to wheat harvest. The main objective of this research was to characterize the sensitivity response of collected littleseed canary grass populations to clodinafop‐propargyl (CP) and isoproturon (IPU) herbicides in whole‐plant dose‐response assays. Among all tested populations, 68 were found to be highly sensitive to CP, whereas all 94 populations were sensitive to IPU. Based on a 50% reduction in shoot dry biomass (GR50 values) and estimated sensitivity index (SI), 26 populations exhibited reduced sensitivity (SI of 2.2–4.4) to CP herbicide. The results also revealed that the littleseed canary grass populations with reduced sensitivity (SI ≥ 2.2) to CP had high sensitivity to IPU herbicide. Overall, these results suggested a high prevalence of littleseed canary grass populations with reduced sensitivity to CP herbicide in Punjab state. Diversified weed management strategies, including the use of alternative herbicides (both preemergence and postemergence), cultural (no‐till drill for wheat sowing and narrow row spacing), and mechanical (cutting of littleseed canary grass panicles prior to wheat harvest) practices should be adopted to control littleseed canary grass populations with reduced sensitivity to CP.