Spotted Anthracnose Vine

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

Vine spotted anthracnose, also called bird's eye, is especially common in case of heavy rains and heavy hail, often leading to various mechanical damage. Attacked by an unfortunate disease, grape shoots become very fragile. By the way, often their defeat by a harmful scourge is confused with hail damage. At the same time, it will not be difficult to distinguish the shoots covered by the disease by the raised and blackened edges of the wounds. And in order not to say goodbye to the harvest of juicy berries, when the first signs of a destructive misfortune are found, one should immediately proceed to active actions

A few words about the disease

On grape leaves attacked by an unpleasant ailment, one can notice numerous necrosis, which look like rounded specks, the diameter of which reaches 1 - 5 mm. All specks are surrounded by brownish-black edges, and sometimes they can differ in rather angular edges. In this case, the affected zones can be single or merge with each other. And the middle of the specks often dry out, staining in grayish-white tones. As for the necrotic tissues, in most cases they fall out of the center of the affected areas, giving them a strongly "perforated" appearance.

Young leaves are most susceptible to infection with a destructive ailment. Most often, specks can be seen along the leaf veins, but sometimes they can cover the leaf blades and the whole. If leaf veins were affected by necrosis (this often happens in young leaves), then the habitual development of leaflets is noticeably disrupted, which in turn leads to the formation of abnormal leaves or to their rapid drying. And the tips of the shoots with young foliage at the same time look shrunken and as if burnt.

As for shoots, young shoots are more susceptible to infection attacks. On them, the formation of merging specks endowed with angular or rounded edges begins, framed by edges from violet-brownish to violet-black color. Shoot necrosis quickly leads to longitudinal and rather strong cracking of the bark, with cracks often deepening up to their center.

Grape clusters are susceptible to unfortunate misfortunes just before flowering and up to the moment when the berries begin to ripen. And in the event that the flowering shoots are pinched by necrosis, the sections of the grape clusters located below will quickly begin to fade.

On berries attacked by spotted anthracnose, specks are formed surrounded by a dark narrow border. Initially, the center of the lesion is purple in color, and after some time it becomes slightly velvety. Well, the berries themselves crack at the same time.

The causative agent of such a harmful ailment is a fungus called Gloeosporium ampelophagum, the conidia of which have the ability to germinate in humid conditions with a fairly wide range of temperatures from two to thirty degrees. The pathogen overwinters, usually in the form of sclerotia or mycelium, either in mummified fruits or in infected shoots.

How to fight

It is recommended to start protective measures against the spotted anthracnose of the vine before the shoots reach a length of ten centimeters. This is done because the harmful disease begins to attack the vine immediately with the onset of early spring.

The first spraying is usually carried out with contact agents based on copper, and then the vineyards are treated with an interval of one and a half to two weeks with such systemic fungicides as Skor, Quadris or Ridomil Gold.

In the event of an unexpected hail, as soon as possible, a thorough additional treatment of the growing grapes with fungicides should be carried out.