Skip to main content
ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #426629
Research Project: Knowledge Based Tools for Exotic and Emerging Diseases of Small Fruit and Nursery Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Characterizing aerial dispersal of Xanthomonas hortorum pv. carotae in central Oregon carrot seed production systems during harvest

Author
item BALDINO, KATELYN - Oregon State University
item HUCKINS, MATTHEW - University Of Utah
item Mahaffee, Walter
item CHANG, ETHAN - Oregon State University
item STOLL, ROB - University Of Utah
item PARDYJAK, ERIC - University Of Utah
item SCOTT, JENESS - Oregon State University
item DUNG, JEREMIAH - Oregon State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2026
Publication Date: 2/2/2026
Citation: Baldino, K.D., Huckins, M.K., Mahaffee, W.F., Chang, E., Stoll, R., Pardyjak, E.R., Scott, J.C., Dung, J.K. 2026. Characterizing aerial dispersal of Xanthomonas hortorum pv. carotae in central Oregon carrot seed production systems during harvest. Plant Disease. https://doi.org/10.1094/PDIS-09-25-1995-RE.
DOI: https://doi.org/10.1094/PDIS-09-25-1995-RE

Interpretive Summary: Bacterial blight in carrot seed production cause significant losses do due international trade barriers against contaminated seed. Unfortunately, there extremely limited options for managing the disease and biannual production cycle means new fields are often planted in close proximity to fields soon to be harvested which appears to result in disease movement from field to field. This research aims to give growers rational criteria for separating fields to reduce field to field movement. A novel sampling device was demonstrated and used to assess pathogen spread during mechanical operations in field. This research will lead to risk assessment models that will enable growers optimize field separation to reduce field to field disease spread.

Technical Abstract: Xanthomonas hortorum pv. carotae (Xhc) is a plant pathogenic bacterium that causes bacterial blight of carrot that impacts international trade due to market restrictions. Since there is little to no tolerance for the pathogen in carrot seed, the crop has overlapping growing seasons, and Xhc has been detected in the air near carrot seed production, an improved understanding of the dispersion pathways is needed. Experiments conducted in central Oregon were designed to characterize the airborne transport of particles dispersing Xhc during harvest events. Debris samples were collected with a novel passive sampling device, the Cascade Settling Trap (CST), that sorted particles into size classes of interest as the particles were deposited out of the air column. CSTs were used during one harvest event in 2021 and three in 2022. Negative binomial regression analysis conducted on data collected in 2022 indicated that particle size and the distance from which particles were sampled can be predictive of the amount of Xhc detected. Burkard samplers were utilized in 2021 and 2022 to quantify airborne Xhc during the growing season and specific events of interest. Meteorological data, in conjunction with the use of optical particle counters, allowed for estimation of concentration of airborne particles and their potential for transport based on real-time meteorological conditions. By developing a more detailed understanding of the aerobiology of Xhc, better risk assessment tools and pathogen management strategies can be employed to assess the potential for these particles to disperse Xhc across varying scales.