Herbicide-resistant barnyardgrass (Echinochloa crus-galli) in global rice production

Barnyardgrass (Echinochloa crus-galli(L.) Beauv.), an annual species of the family Poaceae, is a major weed problem in rice-producing countries throughout the globe. Synthetic herbicides can effectively control this grass in rice paddies, but the development of resistant biotypes after the continuous use of the same active ingredients has led to low herbicide efficacy and yield losses. In this review, a summary of resistant-barnyardgrass cases in global rice production is reported based on data from the International Herbicide-Resistant Weed Database. The first case of resistant barnyardgrass in rice paddies was to the photosystem-II inhibitor propanil in the late 1980s. Eighty-five (85) out of 116 cases in the period from 1986 to 2022 refer to resistant barnyardgrass (E. crus-galli var. crus-galli, E. crus-galli var. formosensis and E. crus-galli var. zelayensis) in 16 countries. Barnyardgrass has been found resistant to acetolactate synthase (ALS) inhibitors (34 cases), acetyl-CoA carboxylase (ACCase) inhibitors (23 cases), photosystem-II inhibitors (11 cases), auxin mimics/cellulose biosynthesis inhibitors (9 cases), very long chain fatty acid inhibitors (6 cases), and microtubule assembly inhibitors (1 case). The majority of all resistance cases reported to the active ingredients penoxsulam, bispyribac-sodium, and imazamox (ALS inhibitors), cyhalofop-butyl and fenoxaprop-ethyl (ACCase inhibitors), propanil (photosystem-II inhibitors), and quinclorac (auxin mimics/cellulose biosynthesis inhibitors). Although target-site resistance with specific mutations has been identified, non-target site resistance mainly through herbicide detoxification is also of great concern increasing the chance of multiple herbicide resistance evolution. Rotation of herbicides should be adopted concerning the modes of action used as well as the application methods to mitigate resistance evolution of this weed in rice paddies.

Automated summary

Barnyardgrass, an annual weed in the Poaceae family, is a significant problem in rice-producing countries worldwide. Continuous use of synthetic herbicides has led to the development of resistant biotypes, resulting in reduced herbicide efficacy and yield losses. This review summarizes the cases of resistant barnyardgrass in global rice production, with 85 out of 116 cases reported between 1986 and 2022. Barnyardgrass has exhibited resistance to various herbicide classes, including ALS inhibitors, ACCase inhibitors, photosystem-II inhibitors, auxin mimics, very long-chain fatty acid inhibitors, and microtubule assembly inhibitors. Non-target site resistance, particularly through herbicide detoxification, poses a significant concern for multiple herbicide resistance evolution. Rotation of herbicides with different modes of action and application methods is recommended to mitigate resistance evolution in rice paddies.