Mehltau

Mehltau, known in English as powdery mildew, refers to a group of fungal diseases that colonize the surfaces of leaves, stems, and fruits on many plants. The causal agents belong to the family Erysiphaceae, with common genera including Erysiphe, Podosphaera, Sphaerotheca and Golovinomyces. The fungi form white to grayish powdery colonies that can cover plant tissues, often starting on the upper leaf surfaces.

Symptoms typically appear as a conspicuous white powdery coating, which may cause leaves to yellow, curl, or become distorted. Severe infections can reduce photosynthesis, vigor, and yield, and can also affect ornamental value. In some cases the infection is more noticeable on young growth or flower buds.

Life cycle and ecology: powdery mildew fungi overwinter as cleistothecia in plant debris or on retired plant material. In favorable spring conditions, they release spores that spread to new tissues. The disease generally favors warm temperatures, moderate moisture on the leaf surface, and poor air circulation; it does not rely on free leaf wetting as much as many other mildews.

Hosts: the disease affects a wide range of crops and ornamentals, including roses, grapes, cucumbers and other cucurbits, apples, and many herbaceous and woody plants.

Management: integrated approaches are used. Cultural measures include pruning for better airflow, avoiding overhead irrigation, spacing plants, and removing infected tissue. Resistant cultivars can help, and sanitation reduces inoculum. When needed, fungicides such as sulfur- or bicarbonate-based products and, if appropriate, systemic fungicides may be applied. Effective management relies on early detection and monitoring within an integrated pest management framework.