Main symptoms

The ESCA is a syndrome characterized by the often irregular expression of symptoms on herbaceous organs such as dyeing of anomalies and dryings and by the presence of vascular disorders and necrosis in the wood, evolving nature (Figures 1 and 2 ). 

Foliar expression of esca

• A slow form characterized by variable discolorations of the leaves, the blade taking a yellow or red tint on white grape varieties, and yellow on black grape varieties (figures 3 to 5). These discolorations may be accompanied by necrotic leaf lesions forming inter-vein digitations causing the tabby appearance of the leaves. (Pictures). If the latter are severely affected, they can dry out completely and detach from the twigs.
  The berries sometimes show a delay in maturity, or wilt (figure 6), or even have small brown or purplish spots on their surface.
• A lightning or apoplectic form at the origin of the wilting and the sudden and total drying out of all the leaves of the diseased vines and leading to their death (figure 7). Note that this event often occurs during the summer after a rainy period followed by strong heat.

Expression in the wood of the esca

A cross section of the vines showing esca leaf symptoms shows various necrotic lesions in the wood :

• the presence of tinder *. Particularly degraded wood has a white “rot”, the color of which can also be yellow or even very light brown. The affected tissues are also tender and friable (Figures 8 and 9);
• of brown lesions central or sectoral **, often associated with tinder (Figure 10). Lesions in a central position may have a dark border or pinkish-brown tissue;
• the black dots ** (Figure 11).

After removing the bark and the surface tissues, it is possible to observe streaks orange-yellow (Figures 12 to 14) in the extension of vine shoots showing leaf symptoms. Note that these vascular lesions are eventually colonized by many opportunistic invaders, including several species of Botryosphaeria spp. It is for this reason that this symptom has been associated with the black dead arm.

It should be noted that the quantity of necrotic lesions present in the strains, their volume and their location favorably influence the leaf expression of esca. 

* Fomitiporia mediterranea is responsible for the amadou, it is a basidiomycete fungus considered a rather secondary colonizer.
** The two pioneer fungi, Phaeomoniella chlamydospora and and Phaeoacremonium aleophilum black punctures , are both responsible for central or sectoral brown necrosis visible in the vines. Let us add that other fungi are often isolated from sectoral necrosis: several species of Botryosphaeria , and sometimes Eutypa lata which is responsible for eutypia.