First report of Eutypella parasitica in Slovenia: addition to the EPPO Alert List
In Slovenia, at the end of May 2005, distinctive oval bark lesions were found on the trunks of Acer pseudoplatanus (sycamore) on Rožnik Hill in the centre of Ljubljana. A characteristic feature of the cankers was that the bark remained in place except at the centre (oldest part of the canker). Cankers were located mostly on the lower portion of the trunk. Intensive surveys around Rožnik Hill revealed that 19 other trees were affected and that the disease was well established, as 3 trees had collapsed. The largest distance between 2 infected trees was 10.6 km, thus suggesting a slow spread. However, it is not known when the disease first appeared. Studies revealed the presence of a fungus which was identified as Eutypella parasitica (morphological and molecular characteristics). So far, E. parasitica was only known to occur in North America. As it is a serious disease of Acer species, the NPPO of Slovenia suggested that it should be added to the EPPO Alert List.
Eutypella parasitica (canker of Acer pseudoplatanus)
Why: In July 2005, the NPPO of Slovenia informed the EPPO Secretariat that a new canker disease of maples (Acer spp.) caused by Eutypella parasitica was discovered near Ljubljana. So far, this fungus was only known to occur in North America where it can cause damage. The NPPO of Slovenia suggested that E. parasitica should be added to the EPPO Alert List.
Where:
EPPO region: Slovenia (found in 2005 near Ljubljana).
North America: Canada (Ontario, Quebec), USA (Connecticut, Illinois, Indiana, Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New York State, Ohio, Pennsylvania, Rhode Island, Vermont, Wisconsin).
On which plants: Acer spp. In North America, it occurs mainly on A. saccharum (sugar maple) and A. rubrum (red maple). It is occasionally found on A. negundo (box elder), A. pensylvanicum (striped maple), A. platanoides (Norway maple), A. pseudoplatanus (sycamore maple), A. saccharinum (silver maple), A. saccharum subsp. nigrum (black maple). In Slovenia, it was found on A. pseudoplatanus and A. campestre (field maple).
Damage: E. parasitica infects trees only through exposed wood tissue (via dead branches or wounds). Mycelium spreads around the infection site creating a perennial and slow growing canker (on average 1-2 cm per year). Due to the slow progress of the fungus, infection is hardly noticeable during the first years. The typical Eutypella canker has a flat or sunken centre, often retaining the dead bark and surrounded by thick callus. Whitish mycelial fans can be observed under the bark at the canker margin. After 5 to 8 years of infection, the fungus produces spores in tiny, black fruiting bodies (stromata with black perithecia or black perithecia alone) that develop in the centres of cankers. On certain hosts (e.g. A. saccharum) the edge of the canker is deformed and bark extensively swollen. The disease can cause tree mortality by girdling the trunk, especially on small trees. Cankers are not only affecting the aesthetic value of the trees, but with the presence of swollen and callused bark, wood quality is reduced and the affected tree is very susceptible to attacks by wood decay fungi and then to wind breakage.
Pictures can be viewed on Internet: http://www.forestpests.org/subject.html?SUB=557
Dissemination: Fruiting bodies release ascospores during rain or irrigation at moderate temperatures and spores are dispersed by wind. Over long distances, trade of plants for planting or wood could spread the disease.
Pathway: Plants for planting, wood of Acer spp.
Possible risks: Acer species (e.g. A. campestre, A. platanoides, A. pseudoplatanus) are important forest and amenity trees in the EPPO region. Few control measures are available against E. parasitica. Affected branches can be pruned, but there is hardly any treatment possible for trunk cankers. In an urban environment, good growth conditions (adequate watering and fertilization) may help trees to resist infection. A preliminary study on the risk of spread of Eutypella canker in Europe (Ogris et al., 2005 paper presented by at the EPPO Conference) showed that a large portion of European forests could be affected by the disease. However, more data would be needed on the abundance of host species in Europe and economic damage in areas where the fungus occurs. It is desirable to avoid further spread of this disease which is a threat to Acer species grown in forests, urban environments and in nurseries.
EPPO RS 2005/176
Panel review date - Entry date 2005-11
Sources
NPPO of Slovenia, 2005-07 – PRA and datasheet (in Slovenian).
Jurc D, Ogris N, Slippers B, Stenlid J (2005) First report of Eutypella canker of Acer pseudoplatanus in Europe. New Disease Reports, http://www.bspp.org.uk/ndr/jan2006/2005-99.asp
EPPO Conference on Phytophthora ramorum and other forest pests (Falmouth, GB, 2005-10-05/07)
Introduction to Eutypella canker by Ogris N and Jurc D. http://archives.eppo.org/MEETINGS/2005_meetings/ramorum_presentations/21_ogris&jurc/Ogris&Jurc1.HTM
Spread risk of Eutypella canker of maples to Europe? by N. Ogris http://archives.eppo.org/MEETINGS/2005_meetings/ramorum_presentations/22_ogris/Ogris1.HTM
Other INTERNET sources:
Canadian Forest Service. Eutypella canker of maple. http://www.glfc.cfs.nrcan.gc.ca/treedisease/eutypella_canker_of_maple_e.html
Pennsylvania State University - Plant Disease Facts. Eutypella Canker on Maple. http://www.ppath.cas.psu.edu/EXTENSION/PLANT_DISEASE/eutypell.html