19. What is botrytis and how does it affect dessert wine?

by Wine

Botrytis is a type of fungus that has a significant impact on the production and taste of dessert wines. It is also known as “noble rot” due to its positive effect on grape production. Botrytis is a beneficial mold that forms on the grapes during humid conditions, and causes them to shrivel and become sweet. This process, known as “passing”, is an essential part of producing many types of dessert wines.

When properly managed, botrytis can produce wines with intense flavors, high sugar concentrations and complexity. The resulting wines are often described as having honeyed, caramel or nutty flavors. These wines can be quite expensive, due to their rarity and labor-intensive production processes.Botrytis, also known as “Gray Mold,” is a fungal disease that affects a variety of plants. It is caused by the fungus Botrytis cinerea and is one of the most common and destructive diseases of many fruits, vegetables, flowers, and ornamental plants.

The fungus thrives in wet, humid conditions and warm temperatures, making greenhouses particularly vulnerable to Botrytis outbreaks. Symptoms vary depending on the plant species infected but are usually characterized by grayish-brown lesions or blotches on plant tissues. In some cases, the lesions may enlarge to form large grayish-brown patches on leaves or stems. Infected fruits may also become shriveled or covered with fuzzy gray growths.

Botrytis can spread quickly through an entire crop if conditions are favorable. For this reason, it is important to take measures to prevent infection in the first place. These include ensuring adequate air circulation around plants, avoiding overhead irrigation whenever possible, and removing any badly infected plant material immediately.

How Does Botrytis Affect Grapes?

Botrytis, also referred to as gray mold, is a type of fungus that is found naturally on grapes. It can cause significant damage to grapes if not controlled, resulting in reduced quality and yield. The fungus affects the grapes by infecting the flowers, stems, leaves and even fruit clusters. It can cause the grape berries to become shriveled and discolored, leading to a decrease in the quality of the crop. Botrytis can also lead to premature ripening and loss of flavor in the grapes.

Botrytis infection is most common when there is a high level of moisture in the air combined with warm temperatures. This combination allows the fungus to spread quickly, infecting more plants and making it difficult to contain. To prevent an outbreak of botrytis, growers must take steps to reduce humidity levels around grapes and ensure they are well ventilated. Proper irrigation techniques can also help control botrytis by preventing water from pooling around plants or accumulating on leaves.

Growers should also monitor their vineyards carefully for signs of infection. If botrytis is detected early enough, it may be possible to treat it with fungicides or other control methods before it causes too much damage. However, once botrytis has had time to spread across a vineyard and affect multiple plants, it will be difficult to contain without significant losses in yield and quality of grapes.

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Types of Botrytis

Botrytis is a fungal disease that affects a variety of plants, including grapes, strawberries, and some ornamentals. There are several different types of Botrytis, and each one is caused by a different species of the fungus. The most common types of Botrytis are gray mold, bull’s-eye rot, and bunch rot.

Gray mold is the most common type of Botrytis and usually affects plants during cool, wet weather. It appears as a grayish-brown growth on plant leaves and stems and can cause the plant to wilt or die if left untreated. Gray mold can also spread to other plants quickly if not controlled.

Bull’s-eye rot is another type of Botrytis that typically affects fruits such as grapes, strawberries, and raspberries. The fungus causes the fruit to develop brown spots that resemble a bull’s-eye pattern. These spots can eventually cause the fruit to rot if not treated in time.

The last type of Botrytis is bunch rot, which usually affects grapes. This type of Botrytis appears as a grayish-brown growth on clusters or bunches of grapes that can spread quickly from one bunch to another if not managed properly. Bunch rot can cause the grapes to become discolored and shriveled and can eventually lead to total crop loss if left untreated.

Botrytis’ Effect on Sweet Wine Grapes

The fungus Botrytis cinerea, also known as ‘noble rot’, is a beneficial fungus that has a significant impact on the production of sweet wine grapes. Botrytis, when present in the right conditions, can cause a dehydration and concentration of grape juice, resulting in an increase in sugar content and intensity of flavor. This infection can also reduce yields but result in higher quality wine grapes.

Botrytis is an opportunistic fungus that thrives when humidity levels are high and temperatures are warm. This makes it particularly prevalent in areas with a Mediterranean climate, such as California’s Napa Valley or France’s Bordeaux region. The fungus will penetrate the grape skins and create small lesions that allow for water to evaporate from the grape pulp. As the grapes dry out, their sugar content increases significantly, resulting in sweeter wines with intense flavors and aromas.

When Botrytis infects grapes, it can also contribute additional aromatic compounds to the wine such as honey, apricot, citrus and even earthy notes. These characteristics make sweet wines produced with botrytised grapes highly sought after by winemakers. This type of wine is usually produced as a dessert wine or late harvest style.

Although botrytis can be beneficial to winemakers who are looking to produce sweet wines with intense flavors and aromas, it is important to note that the effects of this fungus can be unpredictable. If conditions become too humid or wet for too long, botrytis can turn into grey rot which will lead to reduced quality and yields. Therefore, it is important for winemakers to carefully monitor their vineyards for signs of infection so they can take swift corrective action if needed.

In conclusion, botrytis is an important factor for winemakers who are looking to produce sweet wines with intense flavors and aromas. However, if not monitored carefully it can quickly turn from a benefit into a detriment by creating grey rot which will reduce yields and quality significantly.

The Upside of Botrytis

Noble Rot, or Botrytis cinerea, is a fungus that can cause some varieties of grapes to become infected with rot. Although it is typically viewed as a blight, Noble Rot also has some positive effects on wine production. The fungus causes the grapes to become dehydrated, resulting in a more concentrated flavor and aroma. As the grapes become sweeter, they produce higher levels of alcohol and more complex flavors. This can lead to wines that are renowned for their complexity and depth of flavor.

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The infection also helps to reduce the amount of acidity in the wine, creating a smoother finish on the palate. Many winemakers will use Noble Rot to enhance specific wines and create unique flavor profiles. For example, Sauternes is a sweet French dessert wine made from semillon grapes affected by Noble Rot. It is known for its intense aromas and flavors of honey, apricot, and figs.

In addition to producing complex wines with unique flavor profiles, Noble Rot can also help winemakers control production costs and increase yields. The dehydration process caused by the fungus reduces the amount of water in the grape skins which leads to fewer grapes needed to produce a bottle of wine. This can help wineries save money on both labor costs and materials while still producing high-quality wines with unique characteristics.

Overall, Noble Rot can be beneficial in certain cases as it helps produce highly sought-after wines with intense aromas and flavors that are not easily replicated any other way. Although there are risks associated with using this fungus in viticulture, when used responsibly it can lead to delicious results for both producers and consumers alike.

The Role of Climate in Botrytis Infection

Botrytis infection is a fungal disease that affects a wide range of crops. The presence of high levels of moisture and warm temperatures are the primary environmental factors that can lead to an increase in Botrytis infection. This type of fungal disease can cause significant crop losses if not managed properly. Understanding the role of climate in this infection is essential for effective disease management.

The optimal climate for Botrytis infection is moist, warm conditions with temperatures ranging from 15-25°C. High humidity and rainfall also contribute to increased risk of infection by creating a favorable environment for the growth and spread of the fungus. Additionally, exposure to wind or mechanical damage increases the chance of infection by creating wounds in plant tissue that allow the fungus to enter and thrive.

In terms of managing this type of fungal disease, it is important to take proactive steps to prevent it from occurring. This includes avoiding planting crops in areas with high humidity or temperatures, as well as maintaining proper drainage and irrigation practices. Additionally, cultural practices such as pruning dead or dying plant material can help reduce the chances of Botrytis infection. If an outbreak occurs, fungicides may be used to control the spread and reduce crop damage.

Overall, climate plays a major role in Botrytis infection, with moist, warm conditions providing an ideal environment for the fungus to thrive. By understanding the role of climate in this fungal disease, growers can take steps to protect their crops from potential infections through cultural practices and fungicide applications when necessary.

Symptoms of Botrytis in Grapes

Botrytis, or gray mold, is a fungal disease that affects grapes and other fruits. It is caused by the fungus Botrytis cinerea, which thrives in humid and wet conditions. The most common symptom of Botrytis in grapes is the appearance of grayish-brown spots on the fruit’s skin. These spots are often soft and can easily be punctured with a fingernail. As the disease progresses, these spots will grow larger and eventually become dry and leathery. The infected grape berries may also become covered in a fuzzy, gray mold that gives the disease its name.

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Other symptoms of Botrytis include premature ripening, shriveling of the fruit, and reddening of the stems and leaves. If left untreated, this fungal disease can cause significant crop losses. Therefore, it’s important to identify symptoms of Botrytis early on and take steps to prevent its spread. Some preventive measures include avoiding overhead irrigation during flowering and maintaining good air circulation around plants to reduce humidity levels.

Controlling Botrytis Outbreaks

Botrytis, also known as gray mold, is a common plant disease that can cause significant damage to crops. In order to reduce the risk of outbreaks, it is important to understand how the fungus spreads and what steps can be taken to control it.

One of the most effective ways to control Botrytis outbreaks is by controlling humidity levels in the environment. High levels of humidity create ideal conditions for the fungus to thrive and spread quickly. Therefore, it is important to ensure that the environment is kept at low relative humidity levels if possible. This can be done through proper ventilation, use of dehumidifiers and other methods.

Another way to reduce the risk of Botrytis outbreaks is by removing affected plants or crops from the area as soon as possible. This will help prevent the spores from spreading further and causing more damage. Additionally, utilizing fungicides and other chemical treatments may help reduce the risk of an outbreak occurring in the first place.

Finally, it is important to practice good cultural practices such as crop rotation, pruning, and avoiding overcrowding of plants or crops in order to reduce the risk of a Botrytis outbreak occurring. By following these steps, growers can help protect their crops from this damaging fungal disease and maintain healthy yields.


Botrytis cinerea, or “noble rot,” is a naturally-occurring fungus that affects dessert wines such as Sauternes and Tokaji. When properly managed, the fungus can cause dehydration and concentration of the grapes’ sugars, resulting in wines with intense aromas and flavors as well as high levels of residual sugar. While it is possible to produce these types of wines without Botrytis, the unique characteristics it imparts make it an important part of the winemaking process. Botrytis can be a difficult process to manage, but when done correctly, it can result in some of the world’s most delicious dessert wines.

In conclusion, Botrytis is an essential part of producing dessert wines such as Sauternes and Tokaji. Not only does it impart unique characteristics to the wine, but it also allows for increased levels of sweetness and intense flavor profiles. By understanding this process and how to properly manage it, winemakers are able to create some of the most iconic dessert wines in the world.



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