North Carolina Department of Transportation (NC DOT) manages the second largest state supported transportation network in the United States (NC DOT, 2020). To optimally manage vegetation along roadsides, NC DOT utilize herbicides as a component of Integrated Roadside Vegetation Management to ensure safe travel routes for motorists and preserve road system infrastructure. As a result of wide-ranging climatic and edaphic conditions in North Carolina, scenarios may arise that lead to off-target herbicide movement during or following an application along roadsides. With many North Carolina roadsides bordering agricultural production fields, water bodies, wetlands and endangered species habitats, it’s imperative tooptimize applications and develop appropriate best management practices to optimize target efficacy as well as minimizing off-target movement and collateral damage. This is a major concern in many geographic sectors but is paramount in agriculturally diverse states including North Carolina as many crops, particularly high value specialty crops, are extremely sensitive to many herbicides including those used along roadsides in close proximity to agricultural production fields.
North Carolina is the third most agriculturally diverse state nationally and harvested approximately 117,000 acres of flue-cured tobacco accounting for > 70% of total U.S. production valued at > $441 million (USDA ERS 2020). Similarly, 1.52 million acres of soybeans were harvested in North Carolina in 2019 valued at > $468 million positioning tobacco and soybean as the two most economically valuable crops in North Carolina (USDA ERS 2020). Preliminary investigations have evaluated crop sensitivity to commonly used herbicides in terms of visual crop injury; however, additional research is needed to quantify the relationship between visual crop injury and yield reduction as ultimately yield is the most consequential measurement. Further, research is needed to investigate additional variables and their impact on potential herbicide movement as well as characterizing movement from herbicide applications along roadsides via appropriate air sampling techniques.