Crop Clinic

Ragwort populations have been on the increase for many years, and cases of poisoning of livestock show no signs of abating. The spring this may have encouraged emergence of new seedlings and growth of established plants already, but if not, they will start soon.

The risk is always greatest in silage and silage fields should be checked for ragwort rosettes before finally shutting them up. It only needs a single ragwort plant to lethally contaminate a bale of silage.

The problem can occur with hay, but the poison does not spread through the bales quite as readily. It is not recommended to cut infested fields for silage or hay, or to generally attempt spray ragwort before cutting. There is not sufficient time for the ragwort to die back before cutting, and drying ragwort is particularly poisonous. In silage areas, there may still be time to use Barrier H (see below) spot treatment to kill the odd plant, and for it to whither away before cutting.

The most important point about ragwort control is that livestock must be excluded from treated fields for at least 3-4 weeks to allow the ragwort to die back completely. In some cases, this can take even longer: 5-6 weeks. Drying ragwort is deadly, being not only more poisonous, but also more attractive to grazing stock; so do not be tempted to cut corners.

In grazed fields, a general spring spray can give up a good seasons’ control of ragwort, killing both overwintered plants and newly germinated seedlings. Treatment when overwintered plants are at the rosette stage and in active growth (just before stem elongation begins in May) will be most effective. 2,4-D is possibly the most reliable of the single herbicides, but along with MCPA, the other choice, control is often erratic.  Make sure you choose a formulation with a label recommendation for ragwort control – these tend to allow use of a higher dose.

Low populations can be dug-out, but do not just top the ragwort or it may persist and not flower until the following year as a larger plant. Using glyphosate in a wiper or rope-wick system can control flowering plants, but will not control new rosettes, which will not flower until next year.

For a full account of the potential effects of ragwort, and its control is available in a campaign leaflet funded by the Scottish Government and published by SAC: ‘Control that Ragwort’, and a full technical note: TN570 ‘Ragwort Poisoning in Livestock: Prevention and Control’, both available from your SAC Advisory Office.

Simon Oxley