Blumeria hordei is a parasitic fungus specialised on barley. It infects the leaves of its host plants and forms the characteristic white mildew there. Through specialised feeding structures called haustoria it draws nutrients from the plants. For plants the fungus is harmful, and in agriculture an infestation means loss of yield.

Landing. The fungal spores are carried to barley plants by the wind.

Break-in. Adhesive organs (appressoria) pierce the outer waxy layer of the leaf. Finger-shaped feeding organs (haustoria) enter the living cell and withdraw energy-rich carbon compounds and lipids.

Damage symptoms. Early stage: white, cotton-like pustules one to two millimetres across appear on the upper leaf surface and the leaf sheath. Late stage: the coating on the leaves turns greyish brown and the leaf dries out.

Overwintering. Powdery mildew overwinters as mycelium or as resistant fruiting bodies on infected plant residues and volunteer cereals. In spring, spores are released from these and infect new barley plants.

Distribution. Powdery mildew of barley occurs worldwide in all major barley-growing regions. It appears particularly often in dense stands.

Host plants. Powdery mildew affects numerous crop and wild plants, including cereals, grapevines and cucumbers. The various mildew fungi are usually specialised on particular host plants or plant groups.

Prevention and control. Grow resistant varieties; fertilise in a balanced way; keep wide crop rotations and remove infected plant residues; ensure good ventilation of the stand to avoid high humidity.

Economic significance. Economic damage from powdery mildew arises from the reduced photosynthetic performance of the leaves and hence lower yields. Under heavy infection, grain formation and grain quality can be impaired. Crop loss reaches up to 25 percent.

Research into plant–microbe interaction helps to control powdery mildew specifically and can therefore have a positive effect on several UN Sustainable Development Goals.

Goal 2 (Zero Hunger): powdery mildew can affect food security through lower yields and poorer quality of important crops; research may in future yield natural antagonists of the fungus and less susceptible varieties.

Goal 6 (Clean Water and Sanitation): the use of fungicidal sprays against mildew can pollute water bodies; research into natural antagonists can help to reduce the use of chemicals.

Goal 13 (Climate Action): climate change may favour mildew infestations, as warmer temperatures and altered precipitation patterns intensify its spread in many regions.

Blumeria hordei is a parasitic fungus specialised on barley (Hordeum vulgare). It infects the leaves of its host plants and forms the characteristic white mildew there. It can grow only on living plant cells; through specialised feeding structures, the haustoria, it draws water and nutrients from the plant. For plants the fungus is harmful.

Infection proceeds in several steps. The fungal spores are carried to barley plants by the wind. Adhesive organs (appressoria) pierce the outer waxy layer of the leaf; finger-shaped feeding organs (haustoria) enter the living cell and withdraw energy-rich carbon compounds and lipids. In response to infection, the barley relocates its cell nucleus to the infection site — an important part of its immune defence.

At an early stage, white, cotton-like pustules one to two millimetres across appear on the upper leaf surface and the leaf sheath. At a later stage the coating turns greyish brown and the leaf dries out. Under heavy, persistent infection the plant may die. The fungus overwinters as mycelium or as resistant fruiting bodies on infected plant residues and volunteer cereals; in spring, spores are released from these and infect new barley plants.

Powdery mildew of barley occurs worldwide in all major barley-growing regions, and particularly often in dense stands. Powdery mildew as a group affects numerous crop and wild plants, including cereals, grapevines and cucumbers. The various mildew fungi are usually specialised on particular host plants or plant groups.

Economic damage arises from the reduced photosynthetic performance of the leaves and hence lower yields; under heavy infection, grain formation and grain quality can be impaired. Crop loss reaches up to 25 percent. As preventive measures the exhibition names growing resistant varieties, balanced fertilisation, wide crop rotations with removal of infected plant residues, and good ventilation of the stand to avoid high humidity.