Occurrence of Phytophthora citrophthora on Syringa vulgaris in Poland

Abstract

<i>Phytophora citrophora</i> was isolated from dieback shoots, base of diseascd stems and top parts of lilac plants during 3 vegetation periods. The species was detected from about 75% of analysed plant parts. On V8 juice agar and potato-dextrose agar the quickest growth of the species was observed at 25·30°C but development did not occur at 5° and 35°C. Zoosporangia were mostly papillate from spherica1 to ellipsoidal with average dimensions 45.6 x 31.5 μm. <i>P. citrophthora</i> from 5 host plants caused necrosis development of leaves and stem pars of lilac but the quickest spread of disease occurred when plants or their parts were inoculated with isolates from <i>Syringa vulgaris</i> and <i>Pieris japonica</i>. It indicates that the pathogen may be transmissed in nurseries from diseased pieris grown near lilac.