Bacterial blight of carrot, caused by Xanthomonas hortorum pv. carotae (Xhc), is a common seed-borne disease of carrot. The biennial nature of seed-to-seed carrot seed production requires 13 months from planting to harvesting, resulting in a possible “green bridge” that facilitates Xhc survival from year to year. Consequently, the crop is potentially exposed to bacterial blight inoculum from the seedling stage until harvest. The objective of this research was to quantify airborne Xhc during the potential green bridge period in the biennial carrot seed cropping cycle. Burkard 7-day volumetric spore samplers were used to sample air continuously in three fields harvested in 2018 and two fields intended for harvest in 2019. DNA was extracted from Burkard samples and pooled into weekly samples for a quantitative polymerase chain reaction assay specific to Xhc. Xhc was detected in 52 out of 54 weekly air samples at levels ranging from 10² to 10⁶ bacteria/week. Xhc levels in air samples increased from 10² bacteria/week in July to between 10⁴ and 10⁶ bacteria/week at harvest. In contrast, Xhc levels declined from 10⁵ bacteria/week in August to 10³ bacteria/week by November in air samples from one field and varied from 0 to 10⁵ bacteria in air samples from another field. Leaves taken in November showed Xhc populations were between 10³ and 10⁴ bacteria/g leaf tissue, demonstrating that sizeable Xhc populations can be established on seed-to-seed carrot fields prior to winter.