sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDU Faculty of Forestry Journal
Serial: A, Number: Special Issue, Year: 2009, ISSN: 1302-7085, Page: 150-161
SOME MORPHOLOGICAL ASPECTS OF EUTYPELLA CANKER OF
MAPLE (Eutypella parasitica)
ABSTRACT
Nikica OGRIS * , Barbara PIŠKUR, Dušan JURC
Slovenian Forestry Institute, Večna pot 2, 1000 Ljubljana, Slovenia
* nikica.ogris@gozdis.si
Eutypella canker of maple originates from North America and was recently reported
from Slovenia, Austria and Croatia. Disease distribution and frequency in the surveyed
forest stands in Slovenia, Eutypella canker shape and its extent on the trunk, fungi present
in discolored wood, perithecia density, and ascospore discharge were explored. Diseased
maples were usually grouped into infection centers and the disease occurred on 3–5% of all
maple trees at surveyed forest stands. However, incidence up to 30% was recorded. The
canker was usually oval shaped and the average area of the canker was 48% of the affected
part of the trunk. Canker width measured about a half (0.44) of canker length. 54.8% of all
isolates (2,276) from discolored wood were identified as Eutypella parasitica. Perithecia
covered an average of 32% of the total cankered area. A good correlation existed between
the area with perithecia and the whole cankered area. In average, 647,000 perithecia per
canker were found. The average discharge was 506,000 ascospores cm –2 h –1 . One Eutypella
canker discharged from 65 million to 3.3 billion ascospores h –1 , with an average of 1.0
billion ascospores hour –1 under favorable environmental conditions. The inoculation
potential of the fungus is enormous but its rapid colonization of European forests is
prevented by ineffective mode of transmission and slow development of the disease.
Keywords: shape, area, perithecia density, ascospore discharge, frequency, Acer
1. INTRODUCTION
Eutypella canker of maple caused by the fungus Eutypella parasitica R. W.
Davidson & R. C. Lorenz is a well-known disease in North America in the area
around the Great Lakes where it was first found and described (Davidson and
Lorenz, 1938). In Slovenia and Europe, the disease was not reported until 2005
although it seems to have been present for some time prior to this (Jurc et al.,
2006). The disease was also reported from Austria (Cech, 2007) and Croatia (Ogris
et al., 2008). The means of the disease introduction into Slovenia is not known. The
hosts of the disease are maples (Acer spp.). When a disease is introduced to new
location, new hosts can emerge. Similar scenario was observed with Eutypella
canker, when field maple (A. campestre L.) has been found to be a new host of E.
parasitica (Ogris et al., 2005). About 35% of known cankered trees in Slovenia are
field maples. The most susceptible maple in Slovenia is sycamore maple (A.
150