First Report of Powdery Mildew Caused by Erysiphe euonymicola on Euonymus japonicum in Uzbekistan

A new powdery mildew fungus named Erysiphe euonymicola was discovered in the mycobiota of Uzbekistan as a result of a mycological study conducted in the city of Samarkand. This fungus was found on the bush Euonymus japonicum and a brief description along with photographs of Erysiphe euonymicola have been provided. Erysiphe euonymicola is a phytopathogenic fungus that infects 80% - 90% of the leaves and young branches of Euonymus japonicum. The first symptoms of the disease are round, weeping spots on the leaves; later the spots form white mycelium over the entire surface of the leaves. When the plant is heavily infected, both sides of the leaves are completely covered with mycelium. The fungus Erysiphe euonymicola, parasitizing Euonymus japonicum, seriously inhibits the development of the host plant. The mycelium of Erysiphe euonymicola is formed on the surface of the leaf of the host plant and is a cluster of hyphae that form a dense covering in the form of a round spot. Conidiophores are erect, unbranched, and of Pseudoidium type, very variable in shape and size. Conidiophores consist of 2 - 3 cylindrical cells growing vertically from the hyphae; the sizes of conidiophores are given relative to the average length and width of selected conidiophores (n = 15). According to scanning electron microscopy, ellipsoidal-cylindrical conidia are single, scattered among conidiophores, ranging in size from 23.97 to 24.51 × 11.5 to 12.47 µm (n = 15). Conidial stalk cells are usually straight or slightly curved, ranging in size from 23.5 to 23.91 × 7.17 to 7.47 µm (n = 15).