Ragwort – dispelling the myths

Ragwort – Senecio jacobaea is a contentious topic I’ve noticed recently. When ever a photo is posted for identification on different Facebook groups I am following, the comments show a big divide of opinion and the same myths are often used in arguing for its eradication.

For those of you who are unaware of this native plant from the asteraceae family , ragwort is often known for its toxicity to horses and cattle. Some people believe that its toxicity is to be feared and that just by touching it the plant can cause liver failure and so must be removed at all costs – and there has been plenty of media hype to continue this prejudice. However, whilst it is potentially harmful to horses, it also has plenty of benefits to wildlife.

I want to write this because when we moved in last year and the garden was overgrown, there were quite a few ragwort plants in flower around the garden and my first instinct was to go around and pull it all up. I’m glad I didn’t and that I looked into it a little bit, because I later discovered a plant with a few caterpillars of the day-flying cinnabar moth Tyria jacobaeae happily munching away at the leaves. These beautifully distinct larvae with their stripy bodies rely on ragwort as a food plant and without it these critters can not complete their life cycle. Because of the control of ragwort a decline in the numbers of cinnabar moths has been noticed.

Ragwort is also an excellent nectar source for pollinators; bees, butterflies and hoverflies in particular. We had gatekeepers Pyronia tithonus visiting our plants last year which was a new butterfly for me and very exciting. Ragwort is thought to be essential to at least 30 invertebrates, so it really is in my opinion much more of a friend than a foe. This year, I have also planted marsh ragwort Senecio aquaticus around my pond because of how great it is for invertebrates.

2014-07-18 13.33.56

Ragwort control is only really necessary if it occurs in or around a field which is producing hay. This is because ragwort is harmful to horses and they are unable to detect the dried ragwort in hay and the toxicity of the plant remains. Ingestion of dried ragwort can lead to liver failure which is understandably a very good reason to avoid it – although how dangerous it really is is debated given the difficulty in identifying ragwort poisoning as a cause of death. It is also perhaps a good idea to remove it from any grazing paddocks ‘just in case’ even though horses tend to avoid it when it is fresh. We remove it at work when the sheep graze just as a precaution, although I’ve noticed a few plants after they have arrived and the sheep have seemed to avoid them too. It is also worth noting that there is no legislation requiring the removal of ragwort as is often believed. If ragwort is causing a problem then there are powers for an order for removal to be made through the Weeds act 1959, but an order has to be made for this to be enforced.

Ragwort will not harm humans unless perhaps you eat a lot of it. I’ve pulled it up with my bare hands many times with no adverse effects. There is of course the chance that you may be more sensitive to it and for every ten people who are okay with it, there will be one who developed a rash I’m sure.

If you would like to find out more about the truth of ragwort then there is lots of information about it on the internet such as here, here and here. In the meantime, if you find any growing in your garden let it grow and keep an eye out for the cinnabar moth!

“Tyria jacobaeae-04 (xndr)” by Svdmolen – Own work. Licensed under CC BY 2.5 via Wikimedia Commons

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13 thoughts on “Ragwort – dispelling the myths

  1. Thank you for explaining the toxicity of ragwort. It can cause poisoning in cattle which are fed contaminated silage; as you say, ruminants usually avoid the live plant, probably due to the smell. I love cinnabar moths, and have maintained ragwort plants in my suburban garden whenever I see them, as we don’t have too many grazing animals around here! I’m not quite sure I understand you reference to the difficulty in diagnosing equine deaths due to ragwort poisoning. Although hay or haylage with ragwort can cause deaths, most of the horse problems I have seen have been related to poor grazing management, leading to ragwort not being removed, and being the only edible plant left. Blood tests in a live animal can easily detect the liver damage caused as a result of the toxins in the plant. Sadly, there is no cure.

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    • Unfortunately a blood test can only detect general liver damage of which there are many varieties and for which there are a great many causes. Ragwort poisoning causes a form of liver damage called hepatic megalocytosis, this can be detected by autopsy. Unfortunately the presence of hepatic megalocytosis is not diagnostic of ragwort poisoning as it is also caused by aflatoxins, naturally occurring mycotoxins that are produced by Aspergillus flavus and Aspergillus parasiticus. These are species of fungi that grow on damp hay. Unfortunately most diagnoses of ‘ragwort poisoning’ are not reliable as they do not involve autopsy. Of the small number of confirmed cases of hepatic megalocytosis it is not known how many are caused by aflatoxins from mould or pyrrolizidine alkaloids from ragwort. Deciding that any hepatic megalocytosis has been caused by ragwort is unsafe without circumstantial evidence of the source of poisoning, this should consider if mould on hay or silage could be the cause. There have been recent cases of ‘ragwort poisoning’ involving large numbers of cattle but no evidence of ragwort in the field or hay, these may well actually be aflatoxin cases.

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      • Matt is right to point out the difficulties of proving whether ragwort is, or is not, implicated when an animals dies from an illness.
        Acute toxicity is arguably easier to diagnose when evidence of the plant is usually still around as with many welfare cases. Chronic toxicity is not so easy, indeed the insidious nature of PAs is that the damage they cause occurs over extended periods of time. Experiments where animals have been fed controlled diets have shown death from ragwort poisoning can occur months after any of the plant has been eaten though the animal will appear clinically normal until shortly before death.
        Few are calling for eradication of ragwort, all most livestock keepers want is to be able to control ragwort in grazing and fields growing preserved forage, and to prevent it spreading from neighbouring land not in their ownership.
        The Ragwort Code of Practice gives details of landowner/occupier responsibilities and also how to risk assess and judge where ragwort should be removed and where it can be left for invertebrates. Usually removal is only required within 50 m of grazing/forage. For anyone interested in reading more the Code of Practice can be found here: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69264/pb9840-cop-ragwort.pdf

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    • Those of us who are interested in nature and science know that the problem of ragwort has been exaggerated. People with good critical thinking skills know that one should not be too tempted to listen to authority. This is particularly the case with those interested in conserving nature as we all know that the ideas promoted by government in the past have led to the current crisis in biodiversity where for example there has been a massive decline of somewhere around 40% in the numbers of many moth species.

      This is the issue with the Defra Code of Practice,which contrary to the claims of ragwort haters does not place any responsibility on anyone to do anything. It is just guidance and very bad , environmentally damaging guidance at that. The central factor here is the risk and we can say unequivocally that Defra is grossly exaggerating the risk in the way in which they calculate it. We can do this because science and critical thinking give us rules for forming our opinions. ( The same ones that say do not put your faith in the authority of governments or their claims.)

      The statistics are based on claims by an academic at a university animal hospital. First of all Defra make the mistake of believing that you can extrapolate from these figures to get a figure for the whole country, when the rules of science and statistics say that you cannot do that. Secondly, Freedom of Information Requests to the university by myself and others show that the cases do not exist!. So Defra is in effect basing its risk calculations on pseudoscience and falsehoods.

      It is also important to recognise that the academic ( , a well-known campaigning ragwort hater) whose figures are being used by Defra in this nonsensically pseudoscientific calculation of risk has also made a number of other plainly ridiculous claims about our native ragwort. For example, that it was increasing dramatically at a time when it was DECREASING dramatically, that it was causing serious problems in South Africa where the experts tell me there is no record of it ever being recorded , and much to the hilarity of my fellow nature enthusiasts he has been quoted, in a horse care book no less, saying that the Cinnabar Moth, which is declining and requires the alkaloids in ragwort as a feeding stimulus for its larvae, is actually dying off because it is being poisoned by the ragwort that is its natural food!

      The reason that Defra is doing this is because of hysteria generated in horse owners by the distribution of clear falsehoods of which I just gave a small taster above. It is politically motivated as the result of hysteria generated by claims, which are frankly, taken in the round, crazy and not based on rational thinking at all.

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      • I don’t want to get into a tit for tat debate but would simply say
        i) To suggest that anyone promoting proportionate control of ragwort is not interested in nature and science is so inaccurate. This award winning farm does not tolerate ragwort but still manages to help wildlife to thrive: https://www.buglife.org.uk/blog/matt-shardlow-ceo/controlled-life-and-wildlife
        ii)The DEFRA code was drawn up in consultation with a number of groups including Wildlife and Countryside Link – indeed I think Matt was involved in writing some parts of it. Should be read by anyone considering dismissing it purely on hearsay.
        ii) FERA have carried out a review of the evidence concerning ragwort impacts, ecology and control options. It is an interesting read highlighting gaps in the data which require further work. Link is here:
        http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CCwQFjACahUKEwjc86HCwd3GAhWGWBQKHQ_PAs4&url=http%3A%2F%2Frandd.defra.gov.uk%2FDocument.aspx%3FDocument%3D12217_Reviewofevidenceconcerningragwortimpactsecologyandcontroloptions.pdf&ei=TYSmVZyZIoaxUY-ei_AM&usg=AFQjCNFACEaNBIAQMjggqQL1fIXsqyZksA&bvm=bv.97653015,d.ZGU

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      • So right. It is pretty obvious that Defra had an agenda. Just go onto any horsey forum and you’ll see the same bad info circulating. I notice googling that Sue Bebbington has played a role in this.
        I find her arguments very bad as they involve the notion that authority is right something that my science teachers always told me to be aware of. I laughed out loud at the suggestion that Matt Shardlow was responsible for the Code of Practice. Of course he commented but to try to suggest he is responsible is ridiculous.
        I found this comment on the Guardian’s website most informative
        http://www.theguardian.com/environment/2014/jul/31/pulborough-brooks-sussex-shining-blossoms-divide-opinions#comment-38967822

        The point that needs to be made is that ragwort is a valuable plant that is being attacked by people that do not know anything about ecology and science. I read the Code of Practice and it is clearly written from a biased point of view and I agree with Neil about the statistics. You cannot extrapolate in the way in which they have done. It makes a nonsense of the whole document.

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        • Oh dear….!
          I never suggested that Matt Shardlow was responsible for the Code of Practice but he did help to write some parts of it https://twitter.com/MattEAShardlow/status/497510470665142273
          I stand by everything I have ever written and can reassure you I represent no one, not DEFRA, not the BHS – no one.
          I am not influenced by how frequently something is said, who said it, how loudly it shouted or by how much flack I have to take because I hold a counter view.
          I do not believe ragwort should be tolerated in or near grazing or land used to produce preserved forage and I simply want to be able control ragwort if it is judged to be a risk on neighbouring land.
          If you want to dispute the accuracy of anything I have written (and I don’t mean selected edits) I am happy to justify.
          If you simply want to throw insults that’s fine too but it’s hardly positive.

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          • Have been a reader here for a while and at last I really am prompted to log in and reply to this. The item on the Guardian’s website was a very obvious example of someone overreaching themselves in the understanding of the science and getting put right by someone who could read the paper better.
            Sue I bear you no malice. I really don’t, However, if you post items on the internet that are poorly researched. If you then say you won’t listen to anyone who criticises them. if you stop and think, don’t you think it might invite retaliation from people who dislike people who come over as believing themselves all-knowing about a subject where they seem to have big holes in their knowledge.

            Personally I think that Larissa was on her usual excellent form by identifying a good subject on which to blog on. I have on a good few occasions come across people who believe that ragwort is one of the world’s most dangerous plants. Bravo Larissa!

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            • Please don’t misquote me Alan, I clearly didn’t say I won’t listen to anyone. Quite the contrary, I listen to everyone and try my very best not pre-judge based on who said something or how vehemently they make their point – even those considered by some as fools can sometimes say something significant. I would never profess to be ‘all-knowing’ but I definitely know a lot more than I did – and as for the comment “ people who believe that ragwort is one of the world’s most dangerous plants” what is that supposed to imply?
              Would agree with you though that Larissa’s blog is interesting and informative, long may it continue though I doubt I’ll be posting anything anytime soon.

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  2. I’d agree with the horse problem. I’ve lived in a ragwort area for decades, and the only deaths I’ve known of have been starving animals FORCED to eat ragwort to survive. I’ve seen my horses spit it out from hay. My goat nibbles the flower heads off, and he’s ‘a fossil’ in age!

    I do pull it out in pasture, simply because it smothers edible feed grasses. We were part of a control program using beetles. 2 decades ago, the valley was rim to rim yellow in the flowering season. Now, plants can be controlled by pulling, or slashing at the flower head bud stage – to prevent more seed.

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  3. I’ve seen dozens of different invertebrates using Ragwort, either as a nectar source or as a foodplant. During my entomological recording, I’ve seen numerous Diptera using the plant, including six different species of hoverfly – Helophilus pendulus seems to be particularly fond of the flowers when they emerge. Among the more unusual visitors to the flowers I recorded last year was a new Tachinid for my personal species tally, in the form of Eriothrix rufomaculatus. Other Diptera visitors include various metallic soldier flies, including the brassy Sargus species and iridescent green Microchrysa polita.

    I’ve also had some interesting Hymenoptera, such as Lasioglossum calceatum, and no less than five different species of Ichneumon Wasp, though unfortunately these are way beyond my remit to identify.

    Amongst the Lepidoptera, I’ve not only had Cinnabar Moths and Gatekeeper butterflies, but Meadow Brown, Large Skipper, Small Skipper and Five Spot Burnet Moth. Sometimes, Common Blue and Small Copper butterflies are added to the tally as well, and I’ve even had the occasional Holly Blue put in an appearance as well. Ragwort flowers also attract the big showy Nymphalid butterflies – Small Tortoiseshell, Peacock and Comma – and in sheltered zones, the occasional Speckled Wood will also pay a visit.

    I’ve witnessed the occasional Dragonfly using the flower heads as a vantage point for pouncing upon flies, and any aphids that turn up on the plant rapidly attract up to five different species of Ladybird to prey upon them. I’ve seen 7-Spot, 2-Spot, 14-Spot, 10-Spot and Harlequin Ladybird on the plant before today.

    Sadly, one group that seems to avoid the plant is the Hemiptera, at least the conspicuous ones such as Palomena prasina and Dolycoris baccarm (both plentiful in my recording locations), and it’s a pity that I don’t see more of these insects around the plant, though I suspect once I’ve learned to identify Mirid bugs properly, that will change too.

    Incidentally, an earlier flowering species is also present in my locality, in the form of Oxford Ragwort, whose bright yellow flowers and clean, shiny green foliage really deserved a better scientific name than Senecio squalidus. 🙂

    Without Ragwort, much of my entomological recording would be considerably poorer in terms of species diversity.

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