Presence and abundance of airborne Botryosphaeriaceae conidia are governed by temperature and season in the Okanagan Valley, Canada

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BACKGROUND: Grapevine trunk diseases (GTDs) are one of the most important diseases in grapevines, threatening vineyard longevity and productivity worldwide. However, regional patterns of airborne inoculum remain poorly understood for many production areas, including the Okanagan Valley in British Columbia, Canada. Here, we developed and evaluated a droplet digital polymerase chain reaction assay for environmental assessment of Botryosphaeriaceae airborne inoculum. RESULTS: Across 2117 air-sampler extracts from 5 vineyards monitored over 4 years, Botryosphaeriaceae DNA was detected in 41.3% of the samples. At the regional scale, detection frequency and abundance was highest in spring (April-June) and again in summer (July-September). Abundance of inoculum and seasonal timing varied substantially among vineyards and years, indicating strong spatial and time heterogeneity in baseline inoculum pressure. Despite this variability, temperature emerged as a consistent predictor of inoculum presence and abundance. Using a hurdle model with a negative binomial distribution, a positive association between mean temperature during the collection window and both probability of detection and abundance was found. Rainfall and growing degree days did not show a strong effect in inoculum presence or abundance after accounting for seasonality and year-specific effects. CONCLUSION: Together, these findings suggest that Botryosphaeriaceae exposure pressure in the Okanagan Valley is common outside winter months, high-risk periods may differ among vineyards, and simple weather-linked predictors, beginning with temperature, offer a tractable pathway toward regionally grounded risk framing for GTD management decisions. © 2026 His Majesty the King in Right of Canada. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food.

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