The oomycete was described in Japan for the first time. It does not yet occur in Germany. To date, within the EU, it was only detected in Croatia. Up to now it is neither listed in the Annexes of Dir. 2000/29/EC nor at EPPO. Phytophthora chrysanthemi infests Chrysanthemums. It is assumed that P. chrysanthemi would be able to establish in glasshouses in Europe and in the case of suitable climatic conditions possibly also outdoors as demonstrated by the detection in Croatia. Due to its high damage potential for Chrysanthemums P. chrysanthemi poses a considerable phytosanitary risk for Germany and other EU-Member States. Based on this risk analysis, it can be assumed that the pest could establish in Germany or another Member State and would be able to cause severe damage on Chrysanthemums. Hence, measures for the prevention of further introduction of this potential quarantine pest should be met according to § 4a of the Plant Inspection Order. The infestation must be eradicated according to § 4a of the Plant Inspection Order.