A bacterial leaf spot and shoot blight of lavender caused by Xanthomonas hortorum in the UK.
English lavender (Lavandula angustifolia) is grown as a flowering perennial ornamental in UK gardens. It is an important crop for some commercial nurseries that produce large numbers of plants for retail sale in garden centres. During a survey of bacterial diseases of herbaceous perennials in 2010, symptoms consisting of brown to dark brown irregular leaf spots with a water-soaked margin were observed on the leaves of containerised plants growing at one nursery. Approximately 75% of plants were affected and considered to be un-marketable. Based on biochemical, physiological, molecular (sequencing of the gyrB gene) and pathogenicity tests, the causal agent was identified as X. hortorum. This is thought to be the first formal report of a bacterial leaf spot of lavender in the UK caused by X. hortorum.