Pycnidia fungi on Lavender
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Author: Katya Vasileva, Mariana Nakova
In the period 2013 – 2014, a survey was carried out for determining the species of pycnidia fungi which can cause diseases in lavender. From leaves, skeletal branches and stems of lavender plants (Lavandula officinalis L.) with typical symptoms, the species Phomopsis lavandulae and Phoma lavandulae were isolated and identified. On the basis of symptoms and morphological characteristics the fungus Septoria lavandulae was defined. Phomopsis lavandulae attacks stems and leaves. On the leaves elliptical elongated spots were formed, starting from the lamina leaf. On the branches slightly elongated spots to irregular necrotic ones were detected. They developed cracks, the bark split and fell off. The pathogen formed dark colored pycnidia, rounded to slightly pear-shaped, with a diameter of 37.44 – 88.21 х 41.44–104.5 μm. The conidia were colorless, two cellular and elliptical in shape, slightly bent in the middle, with sizes of 6.16 to 8.75 x 2.77–4.55 μm. When Phomopsis lavandulae was associated with Phoma lavandulae and Septoria lavandulae, the damage on the plants increased. Small, yellow-brown spots appeared on the leaves of the plants infected with Phoma lavandulae. They subsequently merged and became necrotic. Yellowish spots formed on the stems, which progressively dried out and became gray-brown. They were filled with pycnidia of the pathogen, which were spherical, brown to black, with sizes of 125.80 x 110.50 μm. Unicellular, colorless, oval to cylindrical spores were formed with sizes of 6.12–5.10 x 1.70–1.36 μm. The symptoms occurring in the plants infected with Septoria lavandulae were well-formed rounded, reddish-brown dark-edged spots on the leaves. The pycnidia of the pathogen were often found on the upper surface. They were immersed in the leaf tissue, spherical, flattened, black, small with a diameter of 41.3–66.7 μm. The conidia were filamentous, straight or slightly curved, with pointed ends, multicellular, colorless, from 12.8 to 33.5 x 1.1–2.6 μm.