Βy Dimitrios Tsitsigiannis, Professor of Plant Pathology, Member of the Governing Council of the Agricultural University of Athens, President of the Mediterranean Plant Pathological Society and coordinator of the STELLA Horizon Project.
Recently, the coordinator of the STELLA Horizon Project was featured in e-thessalia’s news blog, where he discussed the threats facing three emblematic tree species in the mountain Pelion region, the plane, chestnut, and olive trees.
The aim of the blog was to raise awareness and inform readers about the risks posed by tree diseases, the need for early detection and preventive measures, and the importance of protecting these trees as both ecological assets and integral elements of local identity.
Pelion (Greece), the mythical mountain of the Centaurs, is currently facing a silent but devastating threat. Its iconic trees, plane trees, chestnut trees, and olive trees, which are an integral part of its natural beauty and economic development, are being tested by new and emerging diseases that have the potential to irreversibly change the landscape.
Plane trees- the battle against Ceratocystis platani
Since 2003, a plant pathogen called Ceratocystis platani has been wreaking havoc in Messinia in plane trees, causing a disease known as “canker stain ” Over the last 20 years, this fungus has killed thousands of plane trees throughout the country, threatening the tree that symbolises Greek squares and streams and threatening to wipe out all the plane tree forests in Greece. The disease has successively affected the plane tree forests of the Peloponnese, Epirus, Central Greece, Thessaly, and Central Macedonia. In addition to natural plane tree ecosystems, the fungus has also killed a significant number of plane trees in residential areas, where they dominated in squares and adorned streets and recreational areas. Many of these trees were very large and several centuries old.
This pathogen belongs to the harmful quarantine organisms in Europe. Its introduction and spread have led to serious economic damage to local communities, the collapse of local plant capital, and enormous ecological destruction. To date, no officially diagnosed cases of plane tree canker have been observed in Pelion. The fungus is transmitted extremely easily through infected pruning tools, excavation machinery, rivers, and the roots of neighboring diseased trees. In Pelion, where plane trees create beautiful natural green corridors, infection by this fungus could irreversibly change the landscape.
Figure 1: Plane trees, Greece
Credits: Agricultural University of Athens (AUA)
The first symptoms of the disease appear as dark stripes under the tree’s bark and wilting leaves. Early recognition of these symptoms by specialists and citizens is crucial, as it allows for immediate notification of the competent authorities, such as local forestry departments or regional agricultural and plant health services. There is no cure for this disease.
Innovative technologies for detecting plant pathogens.
Modern science offers new hope in the fight against plant diseases. The STELLA research project, involving 14 academic and research institutions as well as small and medium-sized enterprises from Europe and New Zealand, aims to develop integrated digital technologies using drone cameras, satellite imagery, ground proximal cameras, and predictive disease outbreak models to detect early infection outbreaks in forest ecosystems or other crops. At the same time, the project promotes the development of a response strategy based on modern sensor technologies and Artificial Intelligence.
Chestnut tree: The great threat of ink disease
The chestnut tree is also closely associated with the villages of Pelion and can provide a significant source of income for local producers. However, it faces a serious threat that can lead to the death of the trees. Chestnut ink disease is caused by the oomycetes Phytophthora cinnamomi and Phytophthora cambivora, which attack the root system and the base (collar) of the tree. As a result, the tree gradually withers and dies within a few years.
It is recommended to avoid wet or poorly drained soils, as they favor the development of the disease. An environmentally friendly method for managing ink disease is the injection of the harmless active substance potassium phosphite into the tree trunks using special syringes. It is essential to inform chestnut growers about proper water management practices in chestnut orchards and the correct use of both preventive and therapeutic treatments.
Figure 2: Chestnut trees
Retrieved: Shutterstock
Olive tree: The Mediterranean treasure under threat
Olive trees, the most characteristic trees of the Mediterranean, give Pelion a unique landscape on its hills along the Pagasetic Gulf and the Aegean Sea. However, they face significant phytopathological problems that jeopardize the production and quality of olives and olive oil.
Xylella fastidiosa – the big threat. The bacterium Xylella fastidiosa has not been recorded in Greece and is a high-priority quarantine pathogen for the country. It is responsible for the “great destruction” of olive groves in Apulia, Italy, having destroyed more than 21 million olive trees since 2013. In infected olive trees, the bacterium blocks the wood vessels, preventing the transport of water and nutrients. The initial symptoms are leaf scorch (browning along the edges or tips, often with a yellow halo), leaf yellowing, premature leaf drop and finally the trees quickly die. The bacterium is transmitted by sucking insects (leafhoppers) that feed on the sap of the woody vessels. Intensive preventive checks are carried out by the country’s phytosanitary services so that, if it appears, the necessary quarantine measures can be taken in a timely manner.
Figure 3: Olive trees, Attica Region
Credits: Agricultural University of Athens (AUA)
The importance of awareness and cooperation
Safeguarding Pelion’s iconic trees is more than a scientific matter; it is a shared responsibility for all. These cherished trees offer food, shade, breathtaking scenery that attracts visitors, valuable timber, and, above all, lasting memories. Without plane, chestnut, and olive trees, Pelion loses a fundamental part of its identity. Their preservation requires cooperation among scientists, authorities, and citizens. Early detection of symptoms, the implementation of preventive measures, and the adoption of modern digital and artificial intelligence technologies for detecting diseases that threaten the plant ecosystem of Pelion are key to ensuring a green future for the mythical mountain of the Centaurs. Caring for these trees is our responsibility and our legacy to future generations who will admire the beautiful landscapes of Pelion.
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