Main symptoms

Phomopsis viticola is able to attack all the green and growing organs of the vine. Excoriose is especially known for the symptoms it causes on young shoots in the weeks following bud break and on the vine shoots. The lesions observed on these organs are somewhat different depending on their stage of development.

• Young shoots and twigs

Lesions appear on the first internodes at the base of young shoots, often at the level of the lenticels. They are of limited size, elongated in shape, and initially dark in color (figure 1); they turn brown and black subsequently showing bluish reflections (Figure 2). These necrotic lesions frequently become chancery, the central tissues of the cortex thinning and cracking more or less in width (Figures 3 to 7). This last phenomenon is amplified during a period of rapid growth of the vine. Similar lesions can be observed on the petioles and peduncles of inflorescences and racemes. These can lead to the dieback of the bunch, which is then no longer fed, or weakly (figure 8).

In humid conditions, the numerous spots present on the young shoots converge; in the long term, they present broad, more or less extensive and suberized areas, alternating brown areas and lighter areas of suberized tissue. We should add that some more or less strangled shoots, weakened by the presence of basal lesions, can eventually break and / or dry out under the action of the wind or the weight of the bunches of grapes (Figure 9).

As the tissues age, the healing lesions become increasingly corky. Once the shoots are hardened, bleaching of the wood is observed in the fall in addition to necrotic lesions (Figure 10). In addition, many buds have been or are invaded by the mycelium of the fungus, these are all dying buds which will not emerge the following spring.

• Leaves

Tiny irregular to circular, chlorotic and then rapidly dark brown to black lesions develop on the leaves, especially along some primary veins, sometimes secondary (Figure 11). Their size can subsequently reach more than a centimeter in diameter and they often show a more or less marked yellow halo. The stained leaves are often more or less deformed and eventually sifted. In the presence of numerous leaf lesions, large areas of the blade turn yellow, wither, and leaf drop is observed.

• Bunches and berries

Grape berries are also affected; they gradually turn brown and shrivel (Figure 12). 

• Signs

Whatever organs are affected, black punctures pycnidia , , can be observed in damaged tissues and in the epidermis of bleached wood.