Ragwort Fact Sheet
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Ragwort Fact Sheet About Ragwort Common ragwort, or Senecio jacobaea, is one of seven species of ragwort native to the British Isles which may also be known as benweed, staggerweed, tansy ragwort, St James’ wort and stinking Willy. It is abundant throughout Scotland, where it may be seen as yellow flowers on wasteland, beside roads and motorways and on pasture. Despite efforts at control including spraying with herbicide amounts of ragwort have stayed fairly constant at 18% of the grassland area in north-east Scotland where annual surveys were conducted from 19791 and in recent years ragwort has succesfuly colonised roadsides and unmanaged land (like building sites) which has raised its profile as an invasive especies. Ragwort is a member of the family Compositae, as are daisies and dandelions. Young plants are seen as a dense rosette of leaves at ground level, a stem of 60cms to 1m growing over a period of two years. The leaves are dark green, lobed and deeply cut, giving the ragged appearance of its name. Yellow flowers form in close-branched clusters at the tops of the stems from July to September of the second year of growth. The plants spread by large numbers of wind borne seeds which may also fall thickly around the base of the plant. Ragwort is poisonous to horses, cattle and pigs. One of the most common causes of plant poisoning in Britain23 and a major cause of equine liver disease, ragwort is one of a number of plants that contain pyrrolizidine alkaloids (PAs). In the case of ragwort, PAs are present in every part oft the plant. Growing ragwort plants are generally unpalatable, having a bitter taste, and tend to be avoided by grazing animals. Poisoning occurs when plants or seeds contaminate feed, when grazing animals cannot differentiate the early rosettes from grass or when no other forage is available. Dead or cut plants are even more dangerous as they are more palatable and, therefore more likely to be eaten. Most horses appear to eat ragwort as young shoots in the grass at a stage where most owners do not recognise the plant. The effects of PAs are long-term and cumulative. They cause cell necrosis, particularly in the liver, stop cell division for replacement of cells lost to normal wear and tear and damage blood vessels. The main target organ is the liver, but the kidneys and lungs may also be damaged. This means that all ingested ragwort has a damaging effect that will accumulate over a period of time. The exact level of ragwort required to kill a horse is unknown. Signs of ragwort poisoning are usually slow to develop. They may not be visible until the horses has been eating ragwort for weeks or months. It is also possible for signs to appear after the horse has been removed from contaminated pasture or feed. Early signs of poisoning include weight loss, digestive disorders, jaundice and, in some animals, photosensitive dermatitis. This progresses as a chronic wasting disease. Nervous signs may be seen such as restlessness and aimless uncoordinated movement4. The condition has been known as ‘walking disease’ and ‘sleepy staggers’. Affected horses may also appear blind, press their heads against solid objects 5 and become partially paralysed. Death occurs up to six months after the first signs appeared. There is no effective treatment for ragwort poisoning. Horses that appeared to have recovered from an episode of poisoning have proved to have very little stamina, becoming ill if worked 6. Ragwort may be controlled by hand digging, although care must be taken not to allow the plants to come in contact with the skin as PAs are also poisonous to humans! Simply pulling or cutting the plants is ineffective as they can grow from roots left in the ground. The best time to dig ragwort is in the spring and early summer when it is in the rosette stage. At this time it is easily handled and horses have had less time to eat it. Horse owners should make an effort to be able to identify the plant at this stage and also to be able to distinguish between ragwort and other, less common plants. In cases of heavy infestation or over large areas ploughing or spraying with herbicide are recommended. A single spraying may not be sufficient, again due to regeneration of plants from residual roots 7 Horses should not be allowed onto recently sprayed pasture as they are likely to eat the wilted plants. Val Milne 1 Poisonous Plants and Fungi in Britain - Animal and Human Poisoning 2nd edition 1998 Marion R. Cooper & Anthony W. Johnson 2 Anonymous. Veterinary Investigation Diagnostic AnalysisIII 1992 and 1985-92. CeantralVeterinary Laboratory, Weybridge, Surrey UK.1993. 3 Anonymous. Veterinary Investigation Diagnostic AnalysisIII 1994 and 19587-94. CeantralVeterinary Laboratory, Weybridge, Surrey UK.1995. 4 Elcock, L. Oehme, F.W. Senecio poisoning in horses: a summary. Veterinary and Human toxicology 1982, 24, 122-123 5 McGinness, J.P. Senecio jacobaea as a cause of hepatic encephalopathy. California Veterinarian 1980, 34, 20-22. 6 Lessard,P, Wilson,W.D, Olander,H.J, Rogers, Q.R, Mendel, V.E. Clinicopathologic study of horses surviving pyrrolizidine alkaloid(Senecio vulgaris) toxicosis. Am. J. Vet. Res. 19896;47:1776-1780. 7 Ministry of Agriculture, Fisheries and Food. Weed control – Ragwort. AW51. HMSO, London, UK. 1976 (amended 1978).