First report of powdery mildew on Stachys japonica caused by Neoerysiphe galeopsidis in China

Stachys japonica is a traditional Chinese medicinal plant in the Lamiaceae. The roots have proven antipyretic, cough-suppressing, antibiotic, antiphlogistic, and detoxifying effects (Wu and Li 1977). From April to July 2015 and again in 2016, a powdery mildew was observed on 60% of the plants of S. japonica in a nursery facility in Shangqiu, Henan Province, China. Symptoms first appeared as white colonies, which developed into abundant hyphal growth on both sides of the leaves, petioles, stems, and calyces. The yellow, spotty discolorations of infected leaves resulted in wilting and necrosis. Microscopically the conidiophores were 102 to 220 × 9 to 11 μm and produced 2 to 7 immature catenescent conidia. Foot cells of conidiophores were straight, cylindrical, and 26 to 50 μm long, followed by 1 to 3 shorter cells. Conidia were hyaline, cylindrical oval to ellipsoidal, measuring 22 to 32 × 12 to 18 μm (length/width ratio = 1.6 to 2.3) and lacked distinct fibrosin bodies. Hyphal appressoria were lobed to mul...