LAUSR

Xanthomonas fragariae causes strawberry angular leaf spot (ALS), an important disease to the strawberry nursery production industry in North America. To identify potential inoculum sources for ALS, the survival of X. fragariae was examined on the surfaces of eleven common materials found in strawberry nurseries in a designed experiment: corrugated cardboard, cotton balls, cotton cloth (t-shirt), strawberry leaf, sheet metal, plastic, rubber, Tyvek, wood (balsa), glass (microscope slide), and latex (latex glove). Prefabricated 7.62 × 2.54 cm rectangular samples of each material were immersed in a bacterial suspension for 15 min, after which the samples were stored at ~20°C (room temperature) or -4°C (the cold storage temperature for dormant plants in strawberry nurseries) for 1, 3, 7, 14, 30, 60, 90, 180, 270 and 365 days after inoculation (DAI). After the storage period elapsed, bacteria were recovered from the surfaces of each of the samples with PBS-soaked cotton balls at. Survival rate was determined with a viability qPCR procedure and in a plant bioassay that involved rub inoculation of strawberry leaflets with the PBS-soaked cotton balls used to recover bacteria from the samples. Results showed that X. fragariae could survive on all surfaces, but that survival time differed among materials and storage temperature. All materials were capable of harboring viable bacteria up to 7 DAI when stored at -4°C based on the formation of lesions on inoculated leaves in the plant bioassay. The longest survival observed was 270 DAI on cardboard stored at -4°C. At room temperature, cardboard, cotton balls, cotton t-shirt, and strawberry leaf tissue supported small bacterial populations up to 14 DAI. The information from this study can be used to improve sanitation practices for angular leaf spot management in strawberry nurseries.