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EPPO Reporting Service no. 06 - 2017 Num. article: 2017/120

Neonectria neomacrospora an emerging disease of fir trees in Northern Europe: addition to the EPPO Alert List


Why: since 2008, a new and severe canker disease caused by Neonectria neomacrospora (anamorph Cylindrocarpon cylindroides) has been observed on firs (Abies spp.) in Norway. In 2011, the same disease was also found in Denmark causing damage on fir trees. In 2015, the fungus was detected in Southern Sweden. The Panel on Quarantine Pests for Forestry recommended that N. neomacrospora is added to the EPPO Alert List.

Where: the geographical distribution of N. neomacrospora remains to be clarified and it is not entirely clear whether this is a recently emerging fungus in Europe or a re-emerging one. According to the literature, cankers caused by this fungus have probably been observed in North America on A. balsamea as early as the 1930s. However, there is very little information about the current situation of this fungus in North America. In Europe, there are some old records of its presence. In Norway, when the herbarium specimen of the fungus recorded in 1951 under the name Nectria cucurbitula on Abies alba, A. balsamea, A. concolor and A. nordmanniana was re-examined in 1962, it was found to be identical to Nectria cucurbitula var. macrospora (= N. neomacrospora). The anamorph Cylindrocarpon cylindroides was first described from grafted A. concolor in a German nursery more than 100 years ago, but there is no indication that a canker disease caused by N. neomacrospora currently occurs in Germany. In Asia, N. neomacrospora was first found in 2014 in the province of Hubei in China.
EPPO region: Denmark, Norway, Sweden, United Kingdom (an Internet source mentions recent identifications).
North America: Canada (British Columbia), USA (Oregon, Washington).
Asia: China (Hubei).

On which plants: N. neomacrospora has been reported on many Abies species, such as: A. alba (European silver fir), A. amabilis (Pacific silver fir), A. balsamea (balsam fir), A. balsamea var. phanerolepis (Canaan fir), A. cephalonica (Greek fir), A. concolor (white fir), A. durangensis, A. fargesii (Farges's fir), A. fraseri (Fraser fir), A. grandis (grand fir), A. kawakamii (Taiwan fir), A. koreana (Korean fir), A. lasiocarpa (subalpine fir), A. magnifica (Californian red fir), A. nebrodensis (Sicilian fir), A. nordmanniana (Nordmann fir), A. nordmanniana subsp. equitrojani (Turkish fir), A. numidica (Algerian fir), A. pinsapo (Spanish fir), A. procera (noble fir), A. sibirica (Siberian fir), A. vejarii. It has also occasionally been found on Picea abies (Norway spruce), Pseudotsuga menziesii (Douglas fir), and Tsuga heterophila (Western hemlock).

Damage: symptoms are characterized by dead shoots and branches, cankers, branch dieback and heavy resin flow. Under humid conditions, characteristic red perithecia with ascospores (sexual stage) develop on plant material that has been dead for some time (usually more than 1 year). These red fruiting bodies are usually observed in the lower part of the crown and close to the trunk. Conidia from the asexual state (C. cylindroides) can also form on infected bark in humid conditions. In Denmark and Norway, tree mortality has been observed on Abies spp. in landscape plantings, Christmas tree production fields, and forest stands. Studies conducted in Denmark from 2011 to 2014 on 3 trial sites planted with different provenances of A. lasiocarpa have shown that damage has increased significantly. In surveyed sites, the proportion of damaged trees increased from 40% in 2011 to 80% in 2014, and approximately 60% of the trees were seriously damaged. In these studies, it is noted that damage caused by N. neomacrospora was so serious that all A. lasiocarpa provenances from Southern USA included in the trial were rated as unsuitable for Christmas tree production in Denmark.

Dissemination: ascospores are airborne and can spread over long distances. Conidia from the asexual state (Cylindrocarpon cylindroides) can be spread from tree to tree by rain splashes and physical contact between trees. N. neomacrospora is considered to be seed borne, and it has been hypothesized that the fungus has been introduced into Europe via infected seeds.

Pathway: plants for plantings, seeds, Christmas trees, cut branches? of Abies species and other conifer hosts from countries where the fungus occurs.

Possible risks: Abies species are widely grown in the EPPO region for forestry and ornamental purposes, including the production of Christmas trees (e.g. A. nordmanniana and A. lasiocarpa). N. neomacrospora has recently caused severe outbreaks in Denmark and Norway on Abies spp. trees, leading to reduced tree quality and in some cases to tree mortality. N. neomacrospora can attack a very large number of Abies species and subspecies. In nurseries of Christmas tree plantations, some control measures have been recommended (destruction of diseased plants, chemical treatments) but these cannot be applied in forest stands. Studies have been initiated in Denmark to identify resistant or tolerant Abies species and subspecies, but the moment no positive results have been obtained. The epidemic levels which have been observed in Denmark and Norway, as well as the high number of Abies species susceptible to this fungus, indicate that attention should be paid to N. neomacrospora in the cultivation of Abies species.

EPPO RS 2013/234, 2017/120

Panel review date -        Entry date 2017-06

Sources

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INTERNET
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