Powdery mildew of flax

Powdery mildew of flax is a fungal disease caused by the pathogen Oidium lini. This fungus primarily acts as an obligate parasite, infecting the surface of green plant parts and extracting nutrients from the host, which leads to metabolic stress and physiological exhaustion of the flax plant.

The disease affects both fiber flax and oilseed flax crops worldwide. It is a significant concern for agricultural producers in regions with temperate climates where cool to moderate temperatures combined with high humidity create a favorable microclimate for fungal colonization on the plant surface.

Initial symptoms are characterized by white, powdery patches on the leaves. As the infection progresses, these patches expand and cover the stems and seed bolls with a dense, white mycelial mat. Eventually, the infected tissues turn yellow, wither, and prematurely drop, significantly reducing the photosynthetic area of the plant.

Environmental conditions play a critical role in the outbreak of Oidium lini. High relative humidity and the absence of heavy rainfall—which would otherwise wash away the spores—promote the germination and spread of conidia via wind currents. Dense canopy cover and lack of field aeration can exacerbate the severity of the disease.

The economic impact of powdery mildew is substantial, as it leads to a reduction in both fiber quality and seed oil content. Management strategies focus on an integrated approach: using certified disease-free seeds, ensuring proper field drainage, adjusting plant density to improve air circulation, and deploying appropriate fungicides at the first sign of symptoms to protect the crop during its critical growth phases.