Chestnut blight symptoms

Canker can develop on young plants and the symptoms of the early stages of the disease (orange lesions on the bark surface) are then quite specific.  The mycelium is visible to the naked eye under the thick bark of large trees (Figure 1 and 2).

Infected areas of the trunk or tides crack and crumble (Figure 3). Around them, scar-like bulges form, which give the canker its twisted appearance. The fungus starts to develop in the phloem and then reaches the wood. Red fruiting bodies (pycnidia and perithecia) can be observed in the canker for most of the year (Figure 4).

Dieback :

These cankers, known as fast-moving cankers, rapidly cause the upper part to dry out (Figure 5).  Frequently, vigorous shoots form below the trunk cankers.

Healing :

Increasingly, healing or completely healed cankers are observed (Figure 6). In this case, neither dieback of the upper parts nor mortality is observed. This healing is explained by the low aggressiveness of the strains present in these cankers: only the outer tissues are colonised by the fungus, the wood is not affected and the tree's defences allow healing.