Golovinomyces biocellatus on oregano (Origanum vulgare 'Compactum') in Italy.
During January 2011, three-month-old plants of O. vulgare (cv. Compactum) grown in a commercial farm located near Albenga, Liguria, Italy, showed signs and symptoms of an unknown powdery mildew. Ninety percent of the plants were affected. The adaxial leaf surfaces were covered with white mycelia and conidia, while the abaxial surfaces were less infected. As the disease progressed, infected leaves turned yellow, wilted, and eventually fell off. Mycelia were also observed on stems. Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of ribosomal DNA was amplified with the primers ITS1F/ITS4 and sequenced (GenBank accession no. JN594608). The 560-bp amplicon had 99% homology with the sequence of G. biocellatus (GenBank accession no. AB307675).