First report of Melampsora euphorbiae on poinsettia in Norway: addition to the EPPO Alert List
In 2006, an outbreak of Melampsora euphorbiae was observed for the first time in Norway on different cultivars of poinsettias (Euphorbia pulcherrima) in one glasshouse. Rust damage to leaves and bracts was substantial and a large number of plants had to be destroyed with serious economic consequences for the grower. It is not known whether the fungus was introduced on imported cuttings or from infected Euphorbia weed species growing near the glasshouse. M. euphorbiae is common in Norway on wild species of Euphorbia, as well as in many other countries around the world, but so far its occurrence on poinsettias has been reported only in India, Mauritius and Tanzania. Because poinsettia is an important crop in Europe, including Norway where it is the largest flowering potted plant crop with approximately 6 million plants produced every year, the NPPO of Norway suggested that M. euphorbiae should be included in the EPPO Alert List.
Melampsora euphorbiae (a rust of Euphorbia spp.)
Why: In 2006, an outbreak of Melampsora euphorbiae was observed for the first time in Norway on different cultivars of poinsettias (Euphorbia pulcherrima) causing economic damage. Although this rust is known to occur on many wild species of Euphorbia in Europe and other continents, it was the first time that it was reported causing damage to a valuable ornamental crop in Europe. The NPPO of Norway suggested that M. euphorbiae should be added to the EPPO Alert List.
Where: M. euphorbiae is quoted in the literature as a worldwide rust but data is lacking to substantiate its presence in individual countries and the problems it may cause. The following distribution is therefore most likely to be incomplete.
EPPO region: Austria, Germany, Hungary, Italy, Norway, Serbia, Spain, Switzerland, Turkey, United Kingdom.
Asia: China, India, Iran, Pakistan, Oman, Saudi Arabia, Turkey.
Africa: Mauritius, Tanzania, Zimbabwe.
Oceania: Australia, New Zealand.
North America: Canada.
On which plants: M. euphorbiae lives on a large number of wild or cultivated species of Euphorbia (e.g. E. amygdaloides, E. cyparissias, E. esula, E. exigua, E. helioscopia, E. heterophylla, E. hiberna, E. inarticulata, E. lagascae, E. paralias, E. pekinensis, E. peplus, E. rigida, E. seguieriana). On E. pulcherrima (poinsettia) which is apparently the only host of economic importance, the rust has been reported in 4 cases only (i.e. India, Mauritius, Tanzania and Norway). M. euphorbiae is an autoecious rust (completing its life cycle on one host). Some authors have distinguished different formae speciales of M. euphorbiae, each infecting only one or two species of Euphorbia.
Damage: M. euphorbiae causes typical rust symptoms with orange pustules. On poinsettias in Norway, necrotic spots appeared on the upper surface of the leaves with orange spore masses on the lower surface.
Images of symptoms on wild Euphorbia spp. can be viewed on the Internet:
Dissemination: Little data is available in the literature about the biology of M. euphorbiae but as for other rusts, it is likely that spores can be spread by air currents over long distances. Trade of infected plants can also transport the pathogen.
Pathway: Plants for planting of E. pulcherrima (and possibly other Euphorbia species traded for ornamental or medicinal purposes).
Possible risks: M. euphorbiae is obviously a pathogen which can cause severe damage to its host plants. It has even been studied as a potential biocontrol agent of weeds such as E. esula and E. cyparissias in North America. Data is lacking on many aspects of the fungus biology, in particular, it is not clear whether fungal populations occurring on wild Euphorbia species can affect cultivated poinsettias (as host specialization has been suggested in the past). Nevertheless, because poinsettias are valuable ornamental crops in Europe and are subjected to an important international trade, more attention should be paid to the possible presence of M. euphorbiae in crops and on traded plants.
EPPO RS 2008/056
Panel review date: -
Entry date 2008-03
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