{"id":275,"date":"2026-06-18T23:33:17","date_gmt":"2026-06-18T22:33:17","guid":{"rendered":"https:\/\/www.coltivobio.com\/en\/?p=275"},"modified":"2026-06-21T12:33:56","modified_gmt":"2026-06-21T11:33:56","slug":"grapevine-powdery-mildew-erysiphe-necator","status":"publish","type":"post","link":"https:\/\/www.coltivobio.com\/en\/grapevine-powdery-mildew-erysiphe-necator\/","title":{"rendered":"Grapevine Powdery Mildew (Erysiphe necator)"},"content":{"rendered":"

Powdery mildew is a fungal disease that affects grapevines. It is one of the most important and damaging diseases in viticulture. In this technical guide, we will examine the symptoms, biological cycle, control methods, and organic treatments for grapevine powdery mildew.<\/strong><\/p>\n

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Image 1 \u2013 Symptoms of grapevine powdery mildew on leaves.<\/figcaption><\/figure>\n

Identification and damage: what Is wrapevine powdery mildew?<\/strong><\/h2>\n

Powdery mildew, also known as grapevine powdery mildew, is caused by the fungus Uncinula necator<\/em> (Schw.) Burr. (recently reclassified as Erysiphe necator<\/em> (Schw.) Burr.), which represents the sexual stage of the pathogen. Oidium tuckeri<\/em> is the name historically used for its asexual stage.<\/p>\n

This pathogen infects grapevines and is an ectophytic fungus, meaning that it develops on the external tissues of the host plant. Together with grapevine downy mildew<\/a><\/strong> and grey mold (Botrytis cinerea<\/em>), it forms the group of the three most important fungal diseases of grapevines.<\/p>\n

The disease attacks all green parts of the plant, especially leaves and clusters, from spring through summer. On leaves, powdery mildew appears as white-grey patches with a characteristic powdery appearance (image 1). As the infection progresses, leaves may become distorted.<\/p>\n

Grape clusters affected by powdery mildew also develop the characteristic white-grey fungal growth (image 2 and 3). Infected berries often become necrotic in the affected areas, resulting in deformation and reduced growth compared with healthy berries. Cracking may occur, predisposing the berries to secondary infections by Botrytis cinerea<\/em>, Penicillium<\/em>, Aspergillus<\/em>, and other fungi.<\/p>\n

Shoots infected during the herbaceous stage develop extensive dark necrotic lesions resembling irregular brown-black spots, resulting in weaker canes with poor lignification and increased susceptibility to mechanical damage (image 4).<\/p>\n

When the fungus infects dormant buds, the shoots emerging from those buds are often stunted and deformed.<\/p>\n

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Image 2 \u2013 Symptoms of grapevine powdery mildew on clusters, showing abundant mycelial growth. Note the smaller size of infected berries.<\/figcaption><\/figure>\n
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Image 3<\/figcaption><\/figure>\n

Biological cycle of grapevine powdery mildew<\/strong><\/h2>\n

The pathogen can overwinter either as dormant mycelium inside infected buds or as cleistothecia (fruiting bodies containing sexual spores known as ascospores).<\/p>\n

Infections originating from ascospores begin when overwintering cleistothecia release their spores from plant debris on the vineyard floor. This usually coincides with bud break and is strongly influenced by temperature and humidity.<\/p>\n

Under favorable environmental conditions, wind-dispersed ascospores germinate after landing on grapevine leaves. The fungus then produces mycelium, visible as the characteristic white fungal growth, and begins feeding on host cells.<\/p>\n

Subsequently, the mycelium develops conidiophores that produce large numbers of conidia (asexual spores), which are responsible for secondary infections throughout the growing season.<\/p>\n

Infections arising from overwintering mycelium are largely independent of free moisture. Temperature, however, remains a critical factor, with maximum conidial germination occurring between 22 and 28\u00b0C.<\/p>\n

You may also be interested in our technical guide: “How to Control Grapevine Downy Mildew in Organic Farming.”<\/p>\n

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Image 4 \u2013 Powdery mildew symptoms on a grapevine shoot. Dark lesions caused by the fungus are visible on the still-green cane.<\/figcaption><\/figure>\n

Organic control and proper treatments<\/strong><\/h2>\n

Organic control of powdery mildew relies primarily on sulfur-based treatments and several complementary products, including sodium bicarbonate, potassium bicarbonate<\/a>, and the beneficial fungus Ampelomyces quisqualis<\/em>, a well-known antagonist of powdery mildew pathogens.<\/p>\n

When using bicarbonates, care must be taken to avoid excessive concentrations, which may cause leaf burn. These products should be considered supportive tools, as they are generally insufficient when used alone under high disease pressure.<\/p>\n

Sodium and potassium silicates are also used in powdery mildew management. Their activity is mainly based on strengthening leaf tissues and creating a physical barrier that reduces pathogen penetration.<\/p>\n

Among the most recent and effective biological tools for controlling grapevine powdery mildew are:<\/p>\n