Assessment of Digitaria sanguinalis Resistance to Metamifop and Screening of Alternative Herbicides in Dry Direct‐Seeded Rice Fields of Eastern China

ABSTRACT Digitaria sanguinalis is an annual noxious weed in the Poaceae family, and poses a serious threat to rice yields in dry direct‐seeded systems. Metamifop is the primary herbicide for its control, yet resistant populations have increasingly emerged. However, the resistance status of D. sanguinalis to metamifop in key agro‐ecological regions, such as the major rice‐growing areas of Eastern China, remains to be investigated. In this study, we collected 15 D. sanguinalis populations from direct‐seeded rice fields in Eastern China and assessed their sensitivity to metamifop using whole‐plant bioassays. Concurrently, we screened alternative herbicides for efficacy against the most resistant population and evaluated the joint effects and cultivar safety of three promising herbicides following Gowing's method. The results showed that all tested populations exhibited resistance to metamifop, with GR 50 values ranging from 43.13 to 274.25 g a.i. ha −1 and a resistance index of 2.31–14.71. The JSYC‐1 population exhibited the highest resistance and cross‐resistance to cyhalofop‐butyl and fenoxaprop‐p‐ethyl. Bispyribac‐sodium, propanil and quintrione showed good inhibitory effects on the JSYC‐1 population. Binary combinations of these herbicides exhibited additive or synergistic effects against JSYC‐1. Notably, combinations of bispyribac‐sodium with propanil or propanil with quintrione were safe for the tested rice varieties (Ziliangyou 5, Nanjing 9108, Wankennuo 1). Whereas bispyribac‐sodium + quintrione yielded a selectivity index of 1.28–1.85, indicating potential crop phytotoxicity. This research elucidates the current resistance status of D. sanguinalis to metamifop in Eastern China and identifies effective alternative herbicides and combinations. These findings offer technical guidance for the scientific management of resistant D. sanguinalis in dry direct‐seeded rice fields.