Evaluation on eco-biology and tank-mix efficacy of oxyfluorfen for inhibition of susceptible and resistant goosegrass (Eleusine indica) biotypes across four herbicide groups

A heavy infestation of Eleusine indica (goosegrass) threatens vegetable crops. Selective herbicides is the primary control method. However, overreliance on herbicides can lead to multiple herbicide resistance in goosegrass. This study aimed to: (1) identify resistance in goosegrass biotypes to clethodim, quizalofop, glyphosate, and an MSMA plus diuron premix; (2) assess environmental effects on germination and emergence in resistant (R) and susceptible (S) biotypes; and (3) determine optimal herbicide mixtures for control. Field trials and rain shelter experiment confirmed resistance in the R biotype, with resistance levels 15-, 12-, 80-, and 2-fold higher than the S biotype for glyphosate, clethodim, quizalofop, and MSMA plus diuron, respectively, based on dose causing 50% shoot biomass reduction. However, glufosinate, oxyfluorfen, and napropamide provided 100% control. The S biotype germinated more quickly across osmotic potentials (-0 to -0.8 MPa) under alternating temperatures (30/20°C, 35/25°C, 35/20°C), while the R biotype exhibited delayed germination, varying with temperature. The S biotype was more tolerant to osmotic stress. When planted at 0–2 cm, the S biotype had higher emergence in sandy loam, sandy clay loam, and loamy sand soils, while the R biotype showed delayed emergence, influenced by soil texture. Neither biotype emerged from a burial depth of 7 cm. The strongest synergistic effect occurred at a 20:80 oxyfluorfen and glufosinate ratio for the S biotype and a 60:40 ratio for the R biotype applied early post emergence at the 3- to 4-leaf stage. At the 0- to 1-leaf stage, the most effective pre-emergence ratio was 60:40 for both biotypes using napropamide plus oxyfluorfen. These findings highlight fitness penalties associated with resistance, including increased seed dormancy and delayed germination/emergence in the R biotype, complicating management. Integrated strategies should exploit these trade-offs by using inversion tillage to bury seeds deeper than 7 cm. Alternatively, light irrigation or shallow tillage (<7 cm) during fallow periods can stimulate emergence of both biotypes, followed by mechanical or chemical control through post-emergence treatment with glufosinate plus oxyfluorfen and pre-emergence application of napropamide plus oxyfluorfen at optimal ratios.