This research project addressed two primary
objectives: (1) to characterize off-target herbicide movement along North
Carolina roadsides, and (2) to evaluate the impact of simulated herbicide drift
on key crops in the state to inform best management practices that minimize
off-target injury.
Objective I: This study assessed soybean and tobacco response to simulated drift of five roadside herbicides at four rates (0.01x–1x) and six timings at Sandhills Research Station, NC, in 2022 and 2023. In soybean, sulfometuron-methyl and indaziflam caused 20–33% yield loss at pre-planting and planting, while triclopyr caused 76–80% loss post-planting. In tobacco, sulfometuron-methyl caused 16–24% injury pre-planting and, along with triclopyr, at planting. Post-planting, triclopyr and 2,4-D + dichlorprop caused the highest injury (69–76% and 44–53%, respectively). Damage generally increased with rate but was observed even at the lowest rates.
Objective II: Herbicide drift from roadside applications can damage nearby crops. This study evaluated the effects of simulated drift of five common roadside herbicides (sulfometuron-methyl, indaziflam, triclopyr, triclopyr + clopyralid, 2,4-D + dichlorprop) at four rates (0.01x–1x field rate) and six timings on corn and cotton at the Upper Coastal Plain Research Station, NC, in 2022 and 2023. In corn, sulfometuron-methyl caused the most damage, with 70% injury and 76% yield loss when applied 4 weeks after planting. In cotton, pre-plant applications caused minimal injury, but yield loss occurred even with early applications. Post-planting, synthetic auxin herbicides were particularly damaging; 2,4-D + dichlorprop, triclopyr, and triclopyr + clopyralid applied 4 weeks after planting caused 54%, 33%, and 30% yield loss, respectively. Crop damage generally increased with rate, though losses occurred even at the lowest rates.
Experimental
site located at Interstate 540 in Morrisville, NC
Overall, this research provided critical
insights into factors driving off-target herbicide movement and drift impacts
on crop injury and yield. These findings inform best practices for nozzle
selection, formulation choice, application timing, and drift mitigation to
support effective and environmentally responsible roadside vegetation
management in North Carolina.
