Ramularia Leaf Spot

Pathogen

Ramularia collo-cygni

Hosts

The disease affects only winter and spring barley.

Symptoms

Typical symptoms of Ramularia comprise small brown rectangular lesions, often surrounded by a yellow halo. They resemble the spot-form of net blotch. Following high levels of infection, the leaves may senesce rapidly. Lesions are often obvious on dead leaves as black spots. The spores of the fungus are visible on the surface of dead leaves. Ramularia is frequently found in association with other leaf spots such as abiotic sun scorch, physiological leaf spot and spotting caused by damage to the leaf wax following the application of some fungicides.

Life Cycle

Ramularia-life-cycle.jpg

Ramularia can be detected on the seed and within symptomless leaves. The disease can also be dispersed via air-borne spores. Symptoms can develop on dead lower leaves but symptoms are rarely seen on healthy green leaves until after flowering. There may be a stress or physiological trigger for symptoms to develop. The toxin rubellin D is also thought to be produced by the fungus when the barley host is stressed. Under certain light conditions, this toxin causes oxidative stress, leading to plant cell damage and causing typical leaf symptoms.

Importance

Ramularia leaf spot can cause extensive damage to the upper leaves in spring and winter barley once crops have finished flowering. This can cause extensive losses in yield and quality. Yield losses in spring barley can be up to 0.6 tonnes per hectare.

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