How ramularia leaf spot is assessed in Recommended Lists trials is the subject of a new video from AHDB.
Developed to help train Recommended List trial managers, it features Scotland’s Rural University (SRUC) crop protection team leader Neil Havis, who explains how to tell ramularia lesions apart from other foliar symptoms and how to score symptom severity.
In December 2018, AHDB announced it had suspended disease ratings for ramularia because of the strong and poorly understood influence of the environment on disease development in crops.
This year, AHDB plans to run specific trials to improve understanding of the disease. The training video will help standardise the disease assessment procedure.
Catherine Garman, who manages disease research at AHDB, said: “It’s essential that all Recommended List trials are assessed in the same way. Ramularia is particularly difficult to identify and score. This video will help ensure our trials are assessed to the highest possible standards.”
Scoring process
Within the Recommended List trial assessment process, ramularia disease severity is scored on a one to nine scale.
A score of ‘one’ is recorded when crops show no visible symptoms. Conversely, a score of ‘nine’ is recorded when almost all leaves appear necrotic and lesions are present on all leaves.
The scoring data can be used to establish whether robust varietal disease ratings can be produced.
The video follows on from a publication issued by AHDB in 2018. The document includes information on the life cycle of ramularia and control options, as well as images to help with the assessment of disease severity.
The pathogen that causes ramularia – Ramularia collo-cygni – grows from infected seed and moves systematically within both winter and spring barley crops.
Symptoms, which often develop rapidly, appear on dying leaves throughout the season but occur most frequently on upper leaves after ear emergence.
As symptoms are frequently misdiagnosed, the publication illustrates how mature lesions can be distinguished from other foliar symptoms by applying the ‘five Rs’:
- Ringed with yellow margin of chlorosis;
- Rectangular shape;
- Restricted by the leaf veins;
- Reddish-brown colouration;
- Right through the leaf.
The video, publication and information on fungicide resistance management can be accessed on: ahdb.org.uk/ramularia.
