Ragwort (some species of Senecio)
The genus Senecio is in the Daisy family (Asteraceae or Compositae) which comprises over 1000 species. Of the species native to Britain, six are called ‘ragwort’ - S. jacobaea, Common Ragwort, is the species we will deal with here. Along with the five other ‘Ragworts’, native Seneccio spp. include various Groundsels and Fleaworts. Also in the genus are numerous Mediterranean succulents.
Ragwort is a suitable choice to begin this series with because it is an important native plant and it has become politicized so serves as a good way to examine our attitude to nature.
The controversy resides in its toxicity. It, along with all or almost all members of the genus, produce one or more of a particular group of alkaloids which have toxic properties to certain organisms. In fact, the European Food Safety Authority estimates that some 3% of all flowering plants produce alkaloids of this chemical family. Below I discuss in more detail the concept of ‘toxicity.
As we developed previously, biodiversity resides in interconnectedness, in the formation of mutualistic interactions forming an interdependent community of organisms. It follows that a plant with a large number of such interactions is a particularly important constituent of the community. Ragwort is reported to be utilized by some 62 insect species 30 of which are ‘monophagous’ [eats only ragwort] these include 12 beetles 7 flies and 8 moths, one of which is the cinnabar moth. This doesn’t include species that utilise it as a nectar source and it was found to produce more sugar in nectar than any of 60 species that included ‘weed’ and commercial seed mix species. In addition there are 71 reported fungal associates and one ‘mycorrhizal’ associate [fungi that form intricate mutualistic relations with plant roots]. Of course the insect associates will also have predators and since insect larvae have entirely different roles to the adults, potential interactions are multiplied.
This overview clearly shows the importance of ragwort to healthy, diverse pastures. How is it then that the common perception of ragwort is of a ‘noxious weed’ that needs to be eradicated? How can we have developed an attitude that is actually destructive of healthy natural conditions? In this case it can be traced to the equestrian lobby, however the main point here is that this merely reflects an orientation where any inconvenience to human activity trumps stewardship of the natural world.
Data from the UK, France and The Netherlands show there couldn’t be more than a handful of ragweed poisonings of horses per year. The Netherlands reported none over five years. In the meantime, 150 to 200 horses are killed [or put down] whilst racing and about 80 killed in traffic incidents per year in the UK alone. Undoubtedly many die in riding accidents outside of racing.
It’s the same orientation with foxes. Recently there have been calls for a cull of foxes after a child had been bitten. There are roughly 10 fox bites treated in the UK per year. There are 6000 serious dog bites, 3-5 of them fatal, out of almost 250,000 records of treatment, 1500 serious cat bites and some 60 human bites; but no calls to address this.
Our attitude to ‘weeds’ reflects how we see our relationship with nature. It is based on some sort of arbitrary conception of what ‘good nature’ is and what it looks like. It seems to me the source of this wrong image is complicated but grows out of a disengagement with nature since we no longer see man as an animal, as part of nature constrained by natural laws. Additionally, the overwhelming experience with natural systems now is of something degraded by man to such an extent that natural regulation has ceased to be effective. Acting too is an arrogance that we know best and imagine we are no longer subject to natural laws. Well, the climate emergency argues eloquently that we are not above nature. Lastly, there is a moral confusion which allows us to elevate human well-being, no matter how short term or trivial, above any responsibility to the earth itself. These are things we must over-come.
Toxicity in context
A chemical is toxic when it is biologically active and when an organism hasn’t got the means of dealing with it. This is important to understand because if we think in terms of things as being inherently toxic or non-toxic, we lose the ability to evaluate their role. For example, chocolate is toxic to dogs. This is because dogs don’t have the biochemical mechanism to ‘deal with’ Theobromine or caffeine (both alkaloids, by the way) while humans do. Not to get too technical, the Ragwort alkaloids themselves are not toxic but some of the products they are digested into are. Organisms that can metabolize them while avoiding these break-down products are resistant to them. Interestingly, paracetamol is potentially toxic in the same way - Humans have a mechanism to ‘mop up’ its toxic breakdown product so no harm is done.
By direct measurement, horses and cows have been shown to ‘deal with’ up to about 5% of their body weight of Ragwort, goats are resistant. In pastures, horses and cows will only eat it when there is nothing else thus it becomes an husbandry issue. Otherwise, if hidden in hay in large amounts it could pose a risk. Real life data, however, shows that horse fatalities from ingestion of ragwort by any estimate is negligible.
Of suspected ragwort deaths only a proportion are autopsied for liver damage. Even fairly specific liver damage doesn’t mean Ragwort was involved, however. Several fungal toxins, which are not uncommon, produced by microfungi of the genera Penicillium and Aspergillus in the hay or seed crop, in storage after harvest or in silage not properly prepared produce similar liver damage.
Ragwort is one of many important or even essential plants seen as a problem. But the problem is with us, not ragwort. There is little ragwort on the meadow at present due in part to historical eradication programmes. We will in future encourage this important plant so to improve species diversity as we seek to improve the state of the meadow.