oidio

Oidio, commonly known as powdery mildew, is a group of fungal diseases that affect a wide range of plants. The term refers to the asexual forms formerly placed in the form-genus Oidium; modern taxonomy assigns the causal agents to several genera within the order Erysiphales, including Erysiphe, Golovinomyces, Leveillula and Sphaerotheca. Oidio is prevalent in temperate and subtropical regions and can attack leaves, shoots, flowers and fruits.

Symptoms appear as white to gray, talc-like powders on leaf surfaces, often starting on the upper side. Early signs may include small chlorotic spots; as infection advances, leaves can yellow, curl, or become distorted. Heavy infections reduce photosynthesis, weaken plants, and may cause premature leaf fall. On some hosts, fruit or blossoms may show blemishes or russeting.

Powdery mildews are largely host-specific but many species can infect multiple plant groups, including grapes, roses, apples, cucurbits, cereals and ornamentals. They spread by wind-dispersed conidia produced on the leaf surface; sexual structures called chasmothecia form under certain conditions and allow overwintering on plant debris or bark. Unlike mildews that require free moisture, powdery mildews often prefer dry leaf surfaces with moderate humidity.

Management focuses on cultural practices to improve air circulation, remove infected tissues, and plant resistant varieties where available. In gardens and nurseries, sulfur-based products and other fungicides are commonly used, sometimes in combination with biological controls. An integrated approach combines monitoring, preventive planting, sanitation and appropriate chemical or biological treatments based on crop and climate.