1086 Levente KISS 1 *, Adrien BOLAY 2 , Susumu TAKAMATSU 3 , Roger T. A. COOK 4 , Saranya LIMKAISANG 5 , Nosratollah ALE-AGHA 6 , Orsolya SZENTIVA  NYI 1 , Robin J. BOAL 7 and Peter JEFFRIES 8  Plant Protection Institute, Hungarian Academy of Sciences, H-1525 Budapest, P.O. Box 102, Hungary.  Conservatoire et Jardin botaniques de la Ville de Geneve, Case postale 60, CH-1292 Chambesy, Switzerland.  Faculty of Bioresources, Mie University, Tsu 514-8507, Japan.  Central Science Laboratory, DEFRA, Sand Hutton, York, YO41 1LZ, UK.  Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand.  University of Essen, Department of Botany and Plant Physiology, FB-9 Botanik, Universitatstrasse 5, D-45117 Essen, Germany.  Washington State University, Tree Fruit Research, Wenatchee, WA 98801, USA.  Research School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK. E-mail : lkissnki.hu Received 8 March 2002 ; accepted 10 July 2002. Recently, a powdery mildew anamorph infecting snowberry (Symphoricarpos albus) has been reported as a new plant pathogen in several European countries. We report here its occurrence in the UK, Germany and, for the first time, Switzerland. Based on morphological and scanning electron microscope (SEM) patterns, this novel pathogen appeared similar to the anamorph of a common North American powdery mildew, Erysiphe symphoricarpi (syn. Microsphaera symphoricarpi). A phylogenetic analysis of the internal transcribed spacer (ITS) sequences of the ribosomal DNA (rDNA) of an English and a North American snowberry powdery mildew fungus showed that they are conspecific. Ascomata of the pathogen were found only in one European collection, that being in Germany in 2002. The similarity in morphology of the ascomata also confirmed the co-identity of the European and American snowberry powdery mildews. INTRODUCTION Erysiphe symphoricarpi (syn. Microsphaera symphori- carpi) is a common powdery mildew infecting snowberry (Symphoricarpos albus) and other Symphoricarpos spp. in North America (Howe 1874, Braun 1984, 1987, Farr et al. 1989). However, in Europe, where S. albus and other Symphoricarpos species are commonly planted as ornamentals in parks and gardens, powdery mildew infections were not reported on these bushes until the 1980s (Braun 1987). The first European reports of E. symphoricarpi infecting Symphoricarpos came from England and Scotland (BMSFRD records nos 34948 1990, 2608041996, 3466361997 and 5183181999). Recently, E. symphoricarpi has also been reported from Poland (Czerniawska & Madej 1998, Czerniawska et al. 2000). There is also a German record of a powdery mildew infection of S. albus attributed to M. lonicerae (Foitzik 1990), but this is cited as doubtful by Braun * Corresponding author. (1995). These data suggest that S. albus and other Symphoricarpos species, introduced from North Amer- ica, were generally free of powdery mildew in Europe until the late 1980s. Recently, the use of both SEM (Cook, Inman & Billings 1997) and molecular phylogenetic analyses (Takamatsu, Hirata & Sato 1998, Saenz & Taylor 1999, Takamatsu et al. 1999, Mori, Sato & Takamatsu 2000) have led to important advances in the taxonomy of the Erysiphaceae. A major revision of the powdery mildew genera was proposed (Braun & Takamatsu 2000, Braun et al. 2002) in which the genus Erysiphe is now reserved for all the anamorphs of Oidium subgen. Pseudoidium, thus absorbing the old genera of Microsphaera and Uncinula which are now relegated to sections of Erysiphe. Therefore, the correct name for the powdery mildew fungus infecting S. albus in North America is now Erysiphe symphoricarpi. In autumn 1996, we found S. albus bushes heavily infected with powdery mildew in Zu  rich, Switzerland. Powdery mildew had not been previously recorded on Mycol. Res. 106 (9) : 1086–1092 (September 2002).  The British Mycological Society DOI : 10.1017S0953756202006329 Printed in the United Kingdom. Spread of the North American snowberry powdery mildew fungus, Erysiphe symphoricarpi (syn. Microsphaera symphoricarpi ), to Europe