Powdery mildew of grapevine

The causal agent of powdery mildew in grapes is the fungus Uncinula necator (reclassified as Erysiphe necator). It is an obligate biotrophic parasite that infects the epidermis of green tissues, causing severe damage to commercial viticulture globally.

Symptoms initially appear as white, dusty patches of mycelium on the leaves. As the infection progresses, it covers shoots, flowers, and fruit clusters. Infected berries often fail to develop normally, eventually splitting open and becoming susceptible to secondary infections like bunch rot.

The development of this pathogen is favored by warm temperatures, typically ranging from 20 °C to 28 °C. Unlike downy mildew, this fungus does not require free water or rain to spread its spores; high relative humidity and shaded conditions within the vine canopy are sufficient to facilitate rapid disease progression.

The economic impact of Uncinula necator is profound, often leading to total crop loss if left uncontrolled. The fungus significantly reduces vine vigor, decreases photosynthetic efficiency, and ruins the quality of the grapes, making them unsuitable for both fresh market sale and winemaking.

Integrated pest management is crucial for control. Cultural practices such as canopy management improve airflow, reducing the microclimate humidity favored by the fungus. Chemical control relies on sulfur-based treatments and systematic fungicides applied during critical phenological stages, such as pre-bloom and fruit set.

• Improved canopy management and pruning.
• Application of sulfur-based fungicides.
• Use of systemic fungicides for heavy pressure.
• Regular monitoring of vineyard microclimate.