Agriculture

Preventing bait sickness

During the winter period, the vine is pruned dry, a fundamental operation for the correct management of the vineyard. With this operation, the winegrower adjusts the plant's vegetative-productive balance, with direct repercussions on both the yield and the quality of the grapes. When pruning, it is advisable to avoid drastic interventions. Large cuts, wounds or other lesions in the wood can be entry points for a very dangerous fungal disease that attacks vine wood: the esca disease.

What is bait disease?

This disease, long known in ancient Rome, is still poorly understood today with regard to aetiology, pathogenesis and epidemiology. The aetiology of this phytopathy is very complex. To date, the bibliography shows that there are more than five fungi responsible for bait sickness syndrome. Among them, sncreasing importance is attached to Phaemoniella chlamydospora and P. aleophilum; in fact, inoculating these fungi has made it possible to reproduce the symptoms of the disease.

baiting sicknessThese fungi enter the plant only by wounding, preferring old and diseased parts. After entering, the fungi multiply and invade the woody tissues, breaking them down enzymatically. The disease spreads in the vineyard both through the direct action of the mycelium that passes from infected wood to healthy wood, and through the cutting tools used during pruning.

Symptomatology of esca disease

The main veins and the tissues around them remain green, while the chlorotic areas take on a brownish-yellow colouring for white berry varieties or a brownish-red colouring for red berry varieties, thus giving the leaves a characteristic 'tiger-like' appearance.

Symptomatic leaves may remain on the plant for a long time or fall off with the entire stalk. Typical necrotic staining appears on the bunches, wrapped confluent and extensive on the berries; or, due to profound alterations of the woody organs, the bunches dry out and remain attached to the shoots. On the shoots and wood, there is a progressive disintegration of the woody tissues, which first become necrotic and brownish, and then a whitish colour, giving the tissue a spongy and crumbly consistency.

How can bait disease be prevented?

No chemical means of control are possible against bait disease. Prevention is preventive in nature, and is based on the following measures:

  • Use healthy and controlled propagation material;
  • Carry out winter pruning shortly before vegetative regrowth to encourage faster wound healing;
  • Disinfect vines that have suffered frost damage or heavy hailstorms with copper-based products;
  • Disinfect large cuts due to renewal and reconversion of training systems with healing mastics;
  • Identify and mark affected plants in summer and then, at the end of winter during pruning, recognise them and prune them last, in order not to spread the pathogen by cutting tools;
  • Disinfect tools with alcohol or ammonium salts or concentrated copper sulphate when moving from one plant to another;
  • Remove pruning residues, dead or irreparably affected plants from the vineyard;
  • Carry out remedial operations on vines with disease symptoms through 'return cuts';
  • Reaching apparently healthy wood, then cutting the stump until decay or abnormal discolouration is no longer evident;

Biological control

The use of antagonistic fungi, such as the Trichoderma, increase the protection of pruning wounds against the various pathogens that contribute to the occurrence of esca disease. The Trichoderma is a strong coloniser of vine wood in which it quickly establishes itself, creating a biological barrier to the different species of fungus that cause esca disease.

Read also:

Grapevine esca disease: cures and treatments

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