Virginia pepperweed (<i>Lepidium virginicum</i>) control is influenced by developmental stage

Abstract Native to North America, Virginia pepperweed is a winter annual weed in the mustard family (Brassicaceae) found commonly in agricultural crops, roadsides, landscapes, and other undisturbed areas. Known for its peppery taste, Virginia pepperweed has emerged as a troublesome and difficult-to-control weed in and around major row crops in the Mississippi Delta region. Recently, Virginia pepperweed management has become increasingly challenging due to the weed’s ability to survive control measures when applications are made beyond its early rosette stage and high fecundity rates (∼100,000 seeds plant −1 ). Therefore there is a need to develop effective control measures that could reduce the spread of Virginia pepperweed in crop production systems. Greenhouse experiments were conducted in the 2024 season to evaluate the activity of various burndown herbicides labeled for Virginia pepperweed control in row crops. Virginia pepperweed seed was stratified and germinated in a growth chamber, and seedlings were transplanted into pots and kept in a greenhouse. The herbicides tested at the 1X rate were glyphosate at 1,261 g ai ha −1 , glufosinate at 672 g ae ha −1 , 2,4-D at 1,065 g ai ha −1 , and paraquat at 840 g ai ha −1 . Herbicides were sprayed at three growth stages: early rosette, late rosette, and bolting. Virginia pepperweed control was evaluated at 1, 2, 3, and 4 wk after herbicide application (WAA). Shoot dry biomass data were collected at 4 WAA. Application of 2,4-D resulted in 95% to 100% Virginia pepperweed control at all three growth stages. Depending on the growth stage at which herbicides were applied, there was 40% to 50% control with glyphosate, 18% to 47% with glufosinate, and 0% to 71% with paraquat, with 0% biomass reduction at the bolting stage. However, the highest dry biomass reduction (&gt;80%) was observed with 2,4-D applications at the early rosette stage. Herbicide applications at the early rosette stage resulted in maximum Virginia pepperweed control.