AFBI research highlights crown rust as an increasing problem on grass

The recent spell of warm, dry weather has resulted in an increased occurrence of crown rust on perennial ryegrass swards, especially on those retained for a late silage cut.

Crown rust (Puccinia coronata) is characterised by small orange powdery pustules on the leaf surface and is most apparent from late summer to autumn. For many years this disease has been quite widespread in southern parts of the United Kingdom, but it is now more apparent in other areas and has also been seen on swards on the western side of Ireland, from Co Cork in the south as far north as east Co Down.   A distinct feature of this disease is that the orange rust spores readily become attached to clothing, boots and machines which come into contact with it.

Crown rust is most common on swards where there has been a bulk of material built up for autumn grazing or a late silage cut and is more prevalent when the grass is depleted of nutrients. Severe levels of infection can result in reduced grass yield and palatability is adversely affected.

Several approaches can be taken to reduce the risk of crown rust infection including an August or early September application of N fertiliser. The inclusion of white clover into the sward also helps as nitrogen fixed by the clover provides some nutrition to the grass. Swards which have become severely infected should be taken for silage, given a light application of slurry (as it is now too late in the season to apply granular fertiliser) and allowed to recover.

While crown rust has an adverse affect upon production and palatability to grazing livestock, it has no adverse effects on animal health and the persistency of the sward does not seem to be affected. Infection has been so severe in parts of England this year that farmers have had to apply fungicides.

Breeding for Resistance

An alternative approach to preventing crown rust, which is being adopted by AFBI, is to breed varieties which have a natural resistance to the disease. At AFBI Loughgall, crosses are made using highly rust resistant parental plants. Progeny of these are screened at Loughgall and on several locations in England, France and Holland in association with seed specialist company Barenbrug. Out of the many thousands of plants which are evaluated, a small number of the most rust resistant are finally selected and inter-pollinated to produce rust resistant varieties. This will of course take time but it is a long-term solution to the problem and one which highlights the importance of the grass breeding programme at Loughgall which is focussed on addressing aspects of grass growth which are of primary concern to local farmers.

The AFBI programme has already generated several new varieties, such as Rosetta and Dromara which are highly resistant to crown rust and are now being widely used on farms in the Netherlands where crown rust occurs very severely every autumn. More locally, AFBI varieties including Seagoe are very suitable for use, especially in the east of the country where crown rust is more likely to occur.

Looking ahead, it is anticipated that crown rust and leaf spot (Drechslera siccans) will become increasing problems on farms throughout Northern Ireland. Overcoming these problems will require a major breeding effort by AFBI to ensure that high yielding, disease resistant varieties are available for local farms.

Farmers should always use the Recommended List to inform decisions on which grass varieties are most suitable for their particular enterprise.
All commercial enquiries for AFBI varieties should be passed to Barenbrug UK Ltd (contact David Linton, dlinton@baruk.co.uk)

by David Johnston and John Archer Agri-Food & Biosciences Institute, Loughgall, Armagh
 

Notes to editors: 

AFBI carries out high quality technology research and development, statutory, analytical, and diagnostic testing functions for DARD and other Government departments, public bodies and commercial companies.

AFBI's Vision is “Scientific excellence in Northern Ireland …  serving the world”.

All media enquiries to AFBI Press Office.

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