Asphodel Worries

Flowering bog asphodel

Farmers and land managers have been in touch with the Heather Trust over the past few months to express their concerns about the links between sheep disease and wet ground. 

Yellowses has a number of regional names like saut and plochteach, but it is widely known for causing painful symptoms resembling extreme sunburn, as well as the complete loss of sensitive extremities like ears. In extreme cases, sheep are blinded and lambs are killed. Research suggests that the disease is caused when sheep ingest toxins which attack the liver and cause dangerous chemical build-ups in the body, and the culprit responsible for these toxins is widely believed to be bog asphodel.

Asphodel is a native plant found on wet hill ground with a pretty yellow flower which shows mainly after midsummer. Sheep feeding on asphodel during the early summer months are most likely to show symptoms, and the only treatment is currently to restrict grazing where possible. Seriously affected animals can be brought into the shade where their sunburn-like symptoms are less of a problem, but this is seldom practical in the summer months on hill farms where sheep should be getting the benefit of the grass and indoor housing may be unsuitable or non-existent.

The precise relationship between asphodel and yellowses is not totally clear, and many sheep are grazed happily on wet, asphodel-covered hill ground all summer without any ill-effect at all. At the same time, some of the worst areas in Norway can see up to 50% of lambs killed during sunny summers, and the disease can be a real problem for many upland farmers. The picture is confusing, but asphodel has been linked to other diseases in sheep and cattle over the years, and the plant’s latin name (Narthecium ossifragum) reflects the traditional belief that eating it would give sheep brittle bones, although modern thinking tends to relate this symptom with a general shortage of Calcium in the kind of environment where asphodel thrives.

As land managers are encouraged to engage with important peatland conservation and restoration work, the likelihood is that wetter moors will increase the amount of asphodel available for sheep, and research is underway to learn more about how the disease impacts on livestock. At the same time, wetter moors might also be linked to increased challenges to heather coverage, including the prospect of heather beetle outbreaks which are sometimes linked to moisture content. If we are aiming for a wetter future in the uplands, now is the time to find out what the knock-on effects may be for other land uses.

More information on yellowses is available in an article written by the SRUC’s Davy McCracken in the Heather Trust’s annual report from 2016.