Vine botrytis (Botrytis cinerea): what biological treatments?

Present in all the vineyards of the world, Botrytis cinerea is one of the most feared fungi in viticulture. Responsible for gray mold, it alters the quality of grapes and reduces yields. Its development is favored by humidity and injuries on the berries. Faced with quality issues and environmental requirements, organic and natural treatments offer suitable solutions to limit its impact. Discover the treatments and solutions developed by Agrobiotop against this disease.

Botrytis cinerea, a cryptogamic disease

Botrytis cinerea is a fungus that is omnipresent in vineyards around the world. Polyphagous, it attacks a wide range of crops, but it is on vines that it is particularly formidable. Responsible for gray mold, it deteriorates grape clusters, reduces yields and modifies the quality of harvests. Its impact does not stop there: it can also affect grapes after the harvest, whether during transport or storage.

Under certain specific conditions, this same fungus can be sought for a very different phenomenon: noble rot . This process, used for the production of exceptional sweet wines, is based on a controlled evolution of botrytis, which concentrates the sugars and modifies the aromas of the berries.

Regions with a humid and temperate to warm climate offer particularly favorable terrain for its development.

Prevention methods against Botrytis cinerea

Controlling botrytis relies on appropriate cultivation practices that limit the conditions favorable to its development.

• Select less sensitive grape varieties and clones : some varieties have better natural resistance thanks to thicker skin or more airy bunches.
• Adjust the planting density : sufficient spacing between the plants allows for better air circulation.
• Controlling vine vigor : Overly dense vegetation creates a humid environment conducive to the development of the fungus. Balanced management of fertilization and irrigation helps prevent excessive growth.
• Optimize the ventilation of the clusters : suitable pruning and targeted leaf removal promote the penetration of light and the circulation of air.
• Avoid sprinkler irrigation and interventions on wet vines : free water on the grape clusters facilitates the germination of spores and their propagation. Working on dry foliage limits the risk of contamination.

Agrobiotop solutions against vine botrytis

• BENTOBIO  : powder application or foliar spray
• CHITOPROTECT (Chitosan of animal origin)
• YAKAPRO

1 liter CHITOPROTECT + 1 Kg BENTOBIO /100 liters of water / hectare
Attention CHITOPROTECT is not compatible with copper

BENTOBIO is miscible with copper and sulfur.

What are the factors that promote botrytis in vines?

The development of Botrytis cinerea depends closely on environmental conditions and cultivation practices. Certain situations create a particularly favorable terrain for its establishment and propagation.

Suitable climatic conditions

• A temperature between 17 and 23°C .
• A mild and humid spring .
• Humidity above 90% or the presence of free water on the bunches accelerates contamination.
• Episodes of hail and heavy rain cause damage to the berries.

Vineyard factors

• Topography and soil type : Low areas retain more moisture and increase the risk of infection.
• Plant material : Some grape varieties are more sensitive than others. Varieties with thin skin and compact clusters are particularly vulnerable.
• Cultivation management : excessive vigor, dense foliage and compact clusters create favorable conditions for the proliferation of the fungus by maintaining a humid microclimate.

What are the symptoms of Botrytis cinerea on vines?

On the twigs , brown spots form before hardening. Over time, these marks lighten to whitish. Small black protuberances, corresponding to the sclerotia of the fungus, may also be visible on the affected tissues.

On the leaves , the infection begins with wet, red-brown spots, initially located on the edges of the leaf blade. Gradually, these lesions spread inwards and become necrotic. The leaves then take on a shrivelled and burnt appearance, sometimes covered with a characteristic grey felting.

The inflorescences are also affected, with a progressive drying of the flowers. The stalks and peduncles have brown lesions which compromise the circulation of the sap. Peduncular rot can appear and cause the berries to wilt and fall before they ripen.

On grape clusters and berries , sensitivity is greatest after veraison, although contamination may occur earlier. Moist lesions mark the early stages of infection. Subsequently, the berries turn brown and become covered with a grey felt, a distinctive sign of grey rot.

What impact on the quality of grapes and wine?

Botrytis cinerea infestation leads to reduced yields and profoundly changes the characteristics of the grapes. The alteration of the structure of the berries affects their sugar and acid composition, which disrupts the winemaking processes. The natural aromas of the grapes are weakened, making the wine less expressive and less balanced.

Fermentations can be slowed or disrupted by the presence of undesirable compounds from the fungus. This imbalance results in fungal and moldy notes , which detract from the purity of flavors. Red wines are particularly affected, because botrytis changes the stability of pigments, influencing color and texture. An affected grape loses some of its ability to produce rich, structured wines, requiring adjustments during winemaking.

Development cycle of Botrytis cinerea

During the winter, Botrytis cinerea persists in the form of conidia, mycelium and sclerotia . It is found on the vine shoots, stems and mummified berries left on the vine after harvest, as well as on the bark and dormant buds. The soil also constitutes a reservoir where it can persist for several years.

This fungus is not limited to vines. It can also infect weeds and other crops, which promotes its spread and ensures the constant presence of an inoculum ready to attack the vine as soon as conditions are favorable.

At the end of winter, botrytis resumes its activity and begins to produce spores in the form of conidia . These are spread mainly by air and water.

Wounds play a key role in the spread of the fungus. Insects, hail and even splashing water create openings through which conidia settle and penetrate tissues. Mycelium already present on plant debris can also directly infect growing grape clusters, accelerating contamination of the vineyard.

As soon as it reaches a vulnerable tissue, Botrytis cinerea starts its invasion process. It can directly cross the cuticle and the epidermis of the berries, but it also takes advantage of the slightest injury or microfissure to progress.

Once established, it colonizes weakened, senescent tissues or tissues already affected by other pathogens. The presence of diseases such as powdery mildew or the action of pests such as leafrollers further aggravate the situation.

After infection, the fungus develops, forming a visible gray felt: this is gray mold . At this stage, it produces conidiophores loaded with new spores, which will in turn be spread by wind and water.

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