The 'Javart' disease

Javart is the disease caused by Sirococcus castaneae (synonym Diplodina castanea). This weakening pathogen is observed in weakened stands of chestnut trees, on trees that have suffered wounds or various types of dieback.

The fungus develops on the bark of young stems or coppice strands as elongated cortical spots at the base of the stems, corresponding to necrosis of the underlying cambial zone (Figure 1). The bark becomes brownish, cracks and eventually peels off, leaving the wood bare. Depending on the case, the tree's defences are overpowered by the pathogen, which can then girdle the stem and cause it to dry out, or the tree produces successive scarring beads in response to the attack, giving a perennial canker (Figure 2). Propagation occurs from strand to strand in a coppice stand.

Fruiting bodies are visible in the central zone of the necrosis, in the form of pycnidia (small subcortical pustules, 1 mm in diameter), releasing infective spores at maturity. It seems that the fungus can exist in a latent state in the buds, without expressing itself.

Possible confusion

Javart is difficult to distinguish from Coryneum, another weak pathogen, which causes similar trunk lesions when chestnut is stressed.

Cortical lesions on the trunk can be confused with those caused by ink disease, especially if they start at the root level and are not very well developed. It is necessary to take tissue samples for laboratory diagnosis or immunodetection testing in the field.