Esca disease of grapevine is a very common disease found in vineyards. It can be said that there is virtually no vineyard where this disease is completely absent. In this technical guide, we will scientifically explain how to identify and prevent this disease.
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Identification and damage caused by esca disease
Present throughout the world, esca disease is the result of infection by several fungi. Therefore, it is more accurate to describe it as a disease complex rather than a single disease. This complex causes two distinct types of damage to grapevines. The first is tracheomycosis, meaning the blockage of vascular tissues, and the second is wood decay, resulting in the breakdown of infected tissues.
The occasional presence of infected vines within a vineyard should be considered normal and generally does not require particular concern. However, if preventive measures are neglected and unsuitable agronomic practices are adopted, the disease can spread throughout the vineyard and cause significant vine mortality.
The esca disease complex is caused by the fungi Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Eutypa lata, and Botryosphaeria spp., which have been identified by the scientific community as the principal pathogens responsible for vascular infections. The primary fungus associated with wood decay has been identified as Fomitiporia mediterranea.
The disease produces characteristic symptoms on leaves (see photo 1), causing discoloration of the leaf blade that begins between the main veins and progresses toward the center of the leaf without affecting the primary veins. This creates the characteristic symptom known as “tiger stripe symptoms.”
Following these initial symptoms, the leaves begin to dry out completely, accompanied by partial or complete shoot dieback (see photo 2).
This occurs because the blockage of the vascular system by the fungi prevents the vine from transporting water and nutrients properly. The necrotic areas along the leaf margins are caused by toxic compounds produced by the fungi.
The fungi develop both within the main trunk and the secondary arms of the vine. As a result, symptoms may affect the entire plant, eventually leading to death, or only part of the vine when a single arm is infected (Photo 3).
Biological cycle
These fungi enter the vine through various types of wounds, particularly pruning wounds and injuries caused by adverse weather events such as severe hailstorms. For this reason, when the disease is present in the vineyard, proper preventive practices are essential.
Infected vines may remain symptomless for years, making eradication of the disease particularly difficult.
Symptoms may appear on a vine for several consecutive years before eventually causing its death. In other cases, vines that have shown symptoms in previous years may suddenly collapse and die within a single season. This typically occurs during drought years and in mid-summer, when vines are no longer able to cope with the infection.
It is also possible for vines that have shown symptoms for years to stop expressing them and resume normal production, appearing healthy. In such situations, however, these vines may still pose a threat to the vineyard because the pathogens remain present and capable of producing inoculum.
Vines may also become infected in the nursery before planting.
Esca disease management
Management of this disease is primarily preventive and consists of a series of agronomic practices summarized below:
- Removal of dead or severely affected vines.
- Continuous disinfection of pruning tools such as shears and saws.
- Application of copper treatments after severe hailstorms.
- Application of protective wound sealants on large pruning cuts.
- Application of Trichoderma-based products after winter pruning.
Copper has antifungal activity and can help protect vines from pathogen entry following severe winds and hailstorms. Treatments should be applied promptly, ideally within 24 to 48 hours after the damaging event.
Among the most important preventive tools is the use of Trichoderma. This beneficial fungus helps protect vines against fungal pathogens.
Trichoderma can be applied preventively through two different methods. The first involves application through irrigation systems or direct soil inoculation. This primarily protects the root system against soil-borne diseases.
Even more important is the aerial application immediately after pruning. Scientific studies have shown that pruning wounds represent the main infection pathway for esca pathogens. Protecting these wounds with Trichoderma significantly reduces future infections.
The treatment should be carried out immediately after pruning, shortly before bud break, and when average temperatures are at least 10°C.
For partially affected vines where the main trunk remains healthy, the infected arm can be removed. Care must be taken to eliminate all infected wood. Pruning residues should not be left in the vineyard but should be removed and preferably burned.
Young vines suspected of carrying esca pathogens may be treated using hot water treatment by immersing them in water at 50°C for 30 minutes in order to eliminate potential pathogens.