Powdery mildew caused by Golovinomyces biocellatus on lemon thyme (Thymus × citriodorus) 'Aureus' in Italy.
During autumn 2015, a total of 2500 five-month-old potted plants of T. × citriodorus 'Aureus' were grown in a commercial farm located near Albenga (Savona Province, northern Italy). Approximately 10% of the plants showed symptoms and signs of a previously unknown powdery mildew. A white mycelium covered stems and leaves, particularly the adaxial leaf surfaces, and affected tissues turned brown. As the disease progressed, the affected leaves fell off. Based on morphological characteristics, sequence analysis of the rDNA internal transcribed spacer region and pathogenicity, the causal agent was identified as Golovinomyces biocellatus (syn. E. biocellata). This fungus has been reported on Thymus serpyllum in Italy such as in different European countries. G. biocellatus has been reported on Thymus praecox in Germany and in Switzerland. This is thought to be the first report of G. biocellatus on T. × citriodorus in Italy as well as worldwide.