Information is provided on <em>Erysiphe platani</em>, a newly invasive fungus in Ukraine. The anamorph of this North American powdery mildew was first recorded in Ukraine in 1986 on <em>Platanus orientalis </em>in the Nikita Botanical Garden (Crimea). Later, it was found in other localities of the Crimean peninsula, and in Odessa and Odessa region on three species of plane, namely <em>P</em>. × <em>hispanica</em>, <em>P</em>. <em>occidentalis </em>and <em>P</em>. <em>orientalis</em>. Spread of the fungus was epiphytotic. This mildew significantly reduces the ornamental value of plane trees, which are often planted in public open spaces within urban areas of southern Ukraine. Recently, <em>E. platani </em>has formed the teleomorph in this region. Morphologically, the Ukrainian material is slightly different from the species description, viz. appendages are longer (up to 3 times the chasmothecial diam.), often with less compact apices.