Ramularia leaf spot in barley

The ‘Ramularia leaf spot in barley’ factsheet includes information on the life cycle of ramularia and control options. It also includes numerous images to allow ramularia symptoms to be identified and severity scored.

Pathogen

Ramularia collo-cygni

Hosts

The disease affects 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. For information on how to identify mature ramularia lesions, see the 'Management' section.

Life cycle

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.

Management

> Mature ramularia lesions can be distinguished from other foliar symptoms by applying the ‘5Rs’

> In high-risk situations, use a preventative spray at booting (GS45 to GS49)

> Chlorothalonil* should be included in programmes to ensure effective control and slow further spread of resistance to azoles and SDHIs

> Use identification guidelines and look for symptoms late in the season

> Avoid saving seed for re-sowing from heavily infected crops

This video shows how to identify mature ramularia leaf spot symptoms and how to assess symptom severity.

*A decision not to renew the approval of chlorothalonil was made at a meeting of the European Standing Committee on Plants, Animals, Food and Feed on 22 March 2019. Timelines for the withdrawal are yet to be communicated by authorities.

Further information

In October 2018, AHDB held an international ramularia workshop that brought together researchers, plant breeders, agrochemical companies, agronomists and other experts to share their experiences and theories on this challenging disease. For a flavour of discussions and the ways forward identified, see our blog. or read the CPM article.

Ramularia leaf spot in barley

SRUC’s Neil Havis explains how to tell ramularia leaf spot lesions apart from other foliar symptoms and how to score symptom severity.

Use the '5Rs' to identify ramularia symptoms

How to identify ramularia leaf spot symptoms in barley
  1. Rectangular shape
  2. Reddish-brown colouration
  3. Restricted by the leaf veins
  4. Right through the leaf
  5. Ringed with yellow margin of chlorosis

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