Disease affecting silage crops

Published 9 May 14

This week, Chris Duller, independent soil and grassland management specialist, has seen a lot of rhynchosporium disease cases in silage crops. They were triggered by a combination of weather and soil conditions.

Most of this fungal disease appears on older leaves. Typically, it shows up as browning of the leaf, with the brown lesions having a lighter coloured centre. The disease is primarily spread by rain splash onto the lower leaves and encouraged by cool and moist conditions. Italians and diploid perennials are most susceptible, with disease levels worse with high nitrogen-fed crops or crops that are stressed (under fertilised or where the soil is badly compacted).

In an arable situation, barley growers spray fungicides to protect the leaf area and grain yield. In grassland, any benefit gained from controlling its spread will be offset by the damage done driving through the crop.

Where disease levels are high, don’t delay cutting. Aim for a decent wilt and use a quality additive to ensure a quick and effective fermentation. If the disease comes in a grazing sward it may affect palatability slightly and pre-mowing ahead of the cows would be a sensible option.

Strategies to try and reduce the disease:

  • Pay attention to the disease scores for varieties when selecting seed mixtures – some of the Italians are more susceptible than others
  • Avoid heavy slurry applications in February/March
  • Keep swards tight by late season grazing to reduce bare ground and the risks of rain splash
  • Avoid soil damage and compaction
  • Make sure crops are receiving the correct amount of fertiliser to correct pH.