Disease risk in ryegrasses - Dr Debbie McConnell, DairyCo
Grassland diseases can reduce dry matter (DM) yields by around three per cent in the first three years of a ley.
At this time of year, Crown Rust and Dreschlera are the most likely diseases to be seen in swards.
Crown Rust usually occurs in late summer and autumn, particularly in warm, moist conditions when there is dew on the ground in the morning. It can be identified by yellow-orange pustules that spread across the surface of the leaves. Animals reject grass affected by this disease.
Dreschlera is also often apparent at the shoulders of the season, encouraged by cool, wet and humid conditions. Look out for black spots/marks on the leaves.
Maintaining good soil and plant fertility is one way to reduce plant susceptibility to these diseases. There may be some benefit in removing heavy covers or cutting slightly earlier than usual in spring, to reduce the number of harbouring pathogen spores.
However, introducing disease resistance when selecting ryegrass varieties for reseeding is the most effective disease control method. The
Recommended Grass and Clover Lists (RGCL) give each ryegrass a grading on resistance to Crown Rust, Dreschlera and Mildew.
This
RGCL Merchants' Guide has maps showing the high risk areas across England and Wales for the most important grass diseases.
