Invasive Vegetation Management & Treatment Limited

 

Ragwort: The toxic weed spreading through our countryside

By GRAHAM HARVEY 

All across the country their bright yellow flower-heads sway in the breeze like a clutch of gaudy mop-top dolls and their leaves are ragged and dishevelled.

Ragwort is the plant kingdom's greatest exponent of grunge.

This all-too-familiar plant is now in its prime - in pony paddocks, waste ground and alongside railway tracks up and down the land, posing a deadly threat to Britain's horses and ponies. The British Horse Society believes up to 6,500 horses die every year from Ragwort poisoning.

Ragwort - Senecio jacobaea - contains a group of deadly toxins. When eaten by grazing animals, particularly horses, the plant causes severe liver damage and is often fatal. These toxins pass from the gut direct to the liver, where they destroy cells until there are too few left to carry out vital functions. Liver failure is then inevitable. 

Ragwort

Deadly: This pretty wild flower kills up to 6,500 horses a year and is toxic to humans as well

To protect their animals, horse-owners will spend many hours this summer hand-pulling the deadly plants from grazing paddocks.

But the ragwort vigilantes may also be putting themselves at risk. The plant's toxins can be absorbed through the skin or breathed in as pollen grains. Inside the human body, the poisons begin damaging liver cells, a slow and irreversible process leading to cirrhosis, months or even years later.

There's no evidence that these plant-pulling parties have slowed the weed's advance across the British countryside. Each year, ragwort invades new land - its spread aided by the EU's long-running set-aside scheme under which farmland is taken out production and left to wild species.

Botanists estimate that the annual rate of spread is around ten per cent.

The plant may even be more dangerous than was once thought. New research shows the seedlings to be more toxic than the mature plants. Grazing animals instinctively avoid the mature plant. But the long, thin leaves of seedlings are not detected and are often eaten within a mouthful of grass.

With the weed continuing its inexorable march across the countryside, it threatens to take its highest ever toll of Britain's horse population this summer.

For all its sinister attributes, I must confess to a soft spot for this ragamuffin weed. There's a place close to my home where it flourishes - a dry, grassy bank hidden within a stretch of oak woodland, far from grazing pastures. On a bright summer's day, there's no finer sight than the mass of bright, yellow flowers.

It's a sight that once stirred the poet John Clare: "Ragwort thou humble flower with tattered leaves, I love to see thee come and litter gold."

In the Somerset village where I once lived, a new resident included a few sprays of ragwort in her flower display for the church altar. Moments before the service began, they were spotted by the church warden, a farmer, who threw them out. His precipitous action almost provoked a parish incident.

The contempt of country people for what they see as a pernicious weed is evident in the names they once gave to it. Around the country it was variously named as Staggerwort, Stinking Willie and Mare's Fart.

Old-style farmers knew a thing or two about keeping their pastures free of the detested plant. Most were skilled at grassland management: the art of knowing exactly when to allow their livestock into a field and when to take them out again.

With careful grazing, they maintained a tough turf which acted as a barrier to the weed.

In the age of chemical fertilisers and sprays, these traditional grazing skills have been largely lost. Pastures are often overgrazed - livestock are left in a field for too long, so the grass is shaved like a Number One haircut. As a result, the turf is weakened and patches of bare ground start to appear. This is the opportunity the weed needs.

The attack is launched from the "seed bank", the unseen stockpile of potential new plants that lies buried below the soil surface.

A single stalk with its multiple flowers can produce 200,000 seeds in one season. They can survive in the soil for up to 16 years awaiting an opportunity.

The trigger for action is light. When seeds in the upper soil layers are suddenly exposed to sunlight - by moles, worms, rabbit scrapes or the impact of animal hoofs - they spring into life. Soon, another small patch of Britain has been occupied by the tenacious weed.

Though it's of little comfort to horse owners, the onward march of ragwort has a number of environmental benefits. Its leaves provide food for dozens of insects, including 27 species of moth and half-a-dozen beetles.

Pollen from the flowers is collected by bees. The downside is that bees visiting too many ragwort flowers produce honey with measurable amounts of the plant's toxins. So while no one would argue for the eradication of the weed, there's an urgent need to control it.

A promising new strategy for curbing the weed makes use of one of the insects that feed on it. The caterpillars of the cinnabar moth feed only on ragwort. A single brood can devour a whole plant in a day, then march off in search of another one. Over their life cycle, they can consume more than 30 plants.

A collapse in numbers of the cinnabar moth in the late 1980s is thought to be a reason for the subsequent build-up of ragwort.

Scientists are now looking for ways to reestablish a predator/ prey balance between ragwort and the moth. This would offer hope of a longterm curb on ragwort numbers.

In the meantime, there's no real alternative to chemical sprays for horse- owners and livestock farmers who want to keep their pastures safe.

A judicial application of weedkiller will knock out the dangerous seedlings.

This is equally important for grass that's due to be cut for hay or silage. Ragwort is even more dangerous when baled for hay. Cut and dried, it loses its bitterness while retaining the toxins. So a pony, pulling at a rack of sweet meadow hay, is likely to get a lethal dose without the warning of a bitter taste.

It's also worth looking at traditional methods for keeping ragwort out of pastures. By avoiding over-grazing, horseowners can reduce the weed's opportunity to gain a foothold.

Sheep seem able to eat small quantities of ragwort without harm, particularly if they're one of the more traditional breeds.

In my area of west Somerset, there seems to be no shortage of the characteristic yellow flowers. But I have yet to find a single plant on our own steep, gorsey paddock. This I attribute to our small flock of beautiful Exmoor Horn ewes, which appear capable of chomping their way through practically anything that grows out of the ground or in the hedges.

If I ever do find a ragwort plant in the paddock, I shall dig it up - using rubber gloves, of course. But all those that I come across far from grazing areas, I'll leave well alone, knowing that John Clare's "summer gold" is playing a unique part in the rich tapestry that is Britain's wildlife.

 

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