Outbreaks of a new Oidium disease on Euphorbia pulcherrima in Europe
Several countries in Europe have recently reported outbreaks of a new Oidium species on Euphorbia pulcherrima (poinsettia).
In September and October 2001, an outbreak of Oidium sp. was found on Euphorbia pulcherrima at three places in Germany. In Baden-Württemberg and in Bayern, infected plants were found in a display collection of an institute for horticulture. In Bayern, infected plants were also found in a private company which produces pot plants. The infected plants had been grown from rooted cuttings supplied by various companies. The origin of the disease has not yet been identified. It is suspected that the disease was introduced with latently infected cuttings. Action was taken at all places concerned, and further tests have indicated that the infection is no longer present. The situation of this new Oidium sp. on poinsettia in Germany can be described as follows: Transient, action taken.
Recently, a powdery mildew has been found for the first time by the Swedish Plant Protection Service on Poinsettia.
In UK, there has been a number of recent findings on production nurseries of a new powdery mildew (Oidium sp.) on poinsettia which has been considered as the ‘American poinsettia powdery mildew’.
Note: Looking for data on Oidium of poinsettia, the EPPO Secretariat came across a German publication reporting in 1995 an outbreak of this disease in Denmark, in a variety trial of poinsettias of worldwide origin (Motte & Unger, 1995). All infected plants were destroyed. Apparently, no other outbreaks have been reported since.
Motte, G.; Unger, J.G. (1995) [Appearance of powdery mildew (Oidium spp.) on poinsettias (Euphorbia pulcherrima) in Denmark].
Nachrichtenblatt des Deutschen Pflanzenschutzdienstes, 47(1) p 22.
DEFRA web site – A new Poinsettia powdery mildew http://www.defra.gov.uk/planth/poinset.htm
NPPO of Germany, 2002-02.
NPPO of Sweden, 2001-11.