Abstract Herbicide spray drift from roadside application sites poses risks of damaging nearby sensitive crops. The objective of this research was to investigate the impact of five herbicides (sulfometuron‐methyl, indaziflam, triclopyr, triclopyr + clopyralid, and 2, 4‐D + dichlorprop) commonly used to manage roadside vegetation at four application rates (0.01x. 0.05x, 0.1x, and 1x of the field rate) and six application timings (18, 12, and 6 weeks before planting, at planting, and 4 and 8 weeks after planting) on corn ( Zea mays L.) and cotton ( Gossypium hirsutum L.). Field studies were conducted at Upper Coastal Plain Research Station in Rocky Mount, NC, in 2022 and 2023. Although herbicide sensitivity varied by crop species, both species presented higher levels of injury and stunting for application conducted at planting and early post‐planting, and at higher rates. In corn, sulfometuron‐methyl caused the greatest damage. When applied at 4 weeks after planting, this herbicides caused injury of 100% and 48%, and height reduction of 66% and 16%, at 0.1x and 0.01x rates, respectively. In cotton, synthetic auxin herbicides, particularly 2, 4‐D + dichlorprop and triclopyr, were the most damaging post‐emergence. For instance, 2, 4‐D + dichlorprop applied 4 weeks after planting at the 0.01× rate caused 78% injury and 25% height reduction. This study highlights the importance of herbicide selection and application timing when spraying along roadsides to minimize the risk of spray drift damaging nearby corn and cotton fields.
Polli et al. (Thu,) studied this question.