Cryphonectria carpinicola: addition to the EPPO Alert List
Why: During the last two decades, declining Carpinus betulus (European hornbeam) trees have increasingly been reported in the EPPO region. Initial studies conducted in 2015 in Italy identified two causal agents, Anthostoma decipiens and an unknown Endothiella species. In 2021, further studies on isolates obtained from symptomatic C. betulus trees from Austria, Georgia and Switzerland showed that a new fungal species, Cryphonectria carpinicola was associated with hornbeam decline. Re-examination of Italian isolates (initially attributed to Endothiella sp.) confirmed that they also belonged to C. carpinicola. Since then, more reports of the fungus have been made from other Central European countries (Bulgaria, Hungary, Serbia, Slovakia) based on the analysis of both recently collected and preserved isolates dating back to 2007. In 2023, the presence of C. carpinicola was discovered in Japan. The sexual form was described there for the first time, however, in Europe where only the asexual form has been observed, thus possibly suggesting that the area of origin of C. carpinicola is East Asia. Considering the emergence of C. carpinicola in the EPPO region and its probable Asian origin, the EPPO Secretariat thought that it could usefully be added to the EPPO Alert List.
Where: Although, C. carpinicola was described as a new species in 2021, reports of declining C. betulus have been made in the EPPO region since the 2010s, and the presence of C. carpinicola could be confirmed when analyzing dried mycelium which had collected in Bulgaria as early as 2007. In Japan, a fungal strain collected in 1998 from Castanea crenata and initially identified as C. nitschkei (now C. japonica) was shown to be C. carpinicola, 33 years after its collection. During a preliminary field study conducted in 2022, C. carpinicola was identified in small branches of Carpinus sp. fallen on the ground, in the Tengu Highland Forest, Shikoku Island.
EPPO region: Austria, Bulgaria, Georgia, Hungary, Italy, Serbia, Slovakia, Switzerland.
Asia: Japan (Honshu, Shikoku).
On which plants: The main known host is Carpinus betulus, although records have been made on C. japonicus (in Japan) and Carpinus sp. (in Japan and Georgia). There is also one Japanese isolate found on Castanea crenata prior to the formal description of the fungus.
Damage: Symptoms of C. carpinicola resemble those caused by the well-know pathogen, C. parasitica on chestnut (Castanea spp.). Affected Carpinus spp. trees show bark necrosis on stems and branches, yellow-orange fruiting bodies on branches and trunks, branch and tree dieback.
Dissemination: No information is specifically available for C. carpinicola, but as for other Cryphonectria species, it is probable that natural spread of fungal spores occurs via wind and rain, was well as by indirect animal vectors (e.g. birds, mammals, insects). In international trade, the fungus may be carried by host plants for planting commercialized for forestry or ornamental purposes, wood, and bark.
Pathways: Plants for planting, wood and bark of host species from countries where C. carpinicola occurs.
Possible risks: Carpinus betulus is a widespread and ecologically important tree species across temperate Europe. In forests, it occurs in mixed stands with other broadleaf species. In addition, it is widely grown in ornamental nurseries and frequently planted in urban areas. More studies are needed on many aspects of the biology, host range, geographical distribution of C. carpinicola. In particular, its exact role in hornbeam decline needs to be further studied, as C. carpinicola has been reported to be pathogenic on drought-stressed trees in urban environments, and often together with Anthostoma decipiens. However, it is advisable that particular attention is given to this fungus and the potential threat it might present to C. betulus, both in natural and urban environments.
Sources
Cornejo C, Hauser A, Beenken L, Cech T, Rigling D (2021) Cryphonectria carpinicola sp. nov. associated with hornbeam decline in Europe. Fungal Biology 125, 347–356. https://doi.org/10.1016/j.funbio.2020.11.012
Cornejo C, Otani T, Suzuki N, Beenken L (2023) Cryphonectria carpinicola discovered in Japan: First report of the sexual state on Carpinus tree. Mycoscience 64(5), 123–127. https://doi.org/10.47371/mycosci.2023.07.001
Cornejo C, Risteski M, Sotirovski K, Rigling D (2023) Long-term preserved mycelium establishes the presence of Cryphonectria carpinicola in the Balkans and of Cryphonectria radicalis in Bulgaria. European Journal of Plant Pathology 165, 401–405. https://doi.org/10.1007/s10658-022-02613-8
Milenković I, Trifković M, Karadžić D, Jovanović D, Radulović Z, Jung MH, Jung T (2024) First report of Cryphonectria carpinicola on Carpinus betulus in Serbia. Forest Pathology 54, e12882. https://doi.org/10.1111/efp.12882
Papp V, Palla B, Papp D, Németh C (2024) First report of Cryphonectria carpinicola in Hungary and Slovakia (Central Europe). Forest Pathology 54, e12845. https://doi.org/10.1111/efp.12845
Saracchi M, Sardi P, Kunova A, Cortesi P (2015) Potential host range of Anthostoma decipiens and Endothiella sp., agents of hornbeam blight. Journal of Plant Pathology 97(1), 93–97.https://www.jstor.org/stable/24579135