228 - Bracken Control

I am interested how it is that, with such available access to information, we find it so very difficult to establish what it is that we can aver to be truth, to admit what it is we do not know, the extent to which we care enough to go do something about whatever the issue is, how we identify bias among respondents and even what exactly it is that bothers us about such an issue. Here is a case in point:

Following something entirely different, I came across a Facebook page that concerns itself with the control of bracken. The more I read, the more I saw that the people involving themselves are confused about what it is that they are concerned about. Or if not confused, certainly giving me the impression that they are not precise in expressing what it is that bothers them. See how it has developed.

Bracken is a fern typically found on moorland. In Britain it has successfully out-competed characteristic ground-cover plants such as moor grasses, cowberry, bilberry and heathers. Once valued and gathered for use as animal bedding, tanning, soap and glass making and as a fertiliser, bracken is now seen as a pernicious, invasive and opportunistic plant, taking over from the plants traditionally associated with open moorland and reducing easy access by humans. It is toxic to cattle, dogs, sheep, pigs and horses and is linked to cancers in humans.[3] It can harbour high levels of sheep ticks, which can pass on Lyme Disease1. Grazing provided some control by stock trampling but this has almost ceased since foot and mouth over ten years ago. Global climatic changes have also suited bracken well and contributed to its rapid increase in land coverage.

Bracken is a well-adapted pioneer plant which can colonise land quickly, with the potential to extend its area by as much as 1–3% per year. This ability to expand rapidly is at the expense of other plants and wildlife, can cause major problems for land users and managers. It colonises ground with an open vegetation structure but is slow to colonise healthy, well managed heather stands.

Bracken grows well below 600m; it has been observed growing in soils from pH 2.8 to 8.6. Exposure to cold or high pH inhibits its growth. Bracken is a rhizome and these need to be killed off if attempting to eradicate the plant. thus one needs a systemic herbicide. Asulam will (of course) damage similar plants.

Is Bracken a bad thing? Clearly there is an assumption that this is so.

..in the UK, bracken is thought to cover at least 1.5 million hectares and there is a general view that the area is expanding. .source

The micro-climate found within a bracken-filled space encourages some specific plants and insects. This is not a concern, what is the concern is the change brought about by bracken spreading.  Bracken is difficult to displace because it produces allelopathic chemicals (another way of saying it is difficult to displace, see), which remain active in the soil even after the bracken itself is removed.

I cannot find any other reasons for wanting to remove bracken except that it prevents the growth of other stuff. But since that includes productive plants, too, that seems sufficient for local control on farming land. I shall interpret the context of moorland as one of reducing biodiversity, for which we seem to have consensus that this is a Bad Thing. We certainly have issues with bracken on farmland and on SSSIs, which are in some sense contracted to be rich in diversity; given that bracken is widespread, it could easily be argued that there should be very little bracken on any SSSI. Since SSSIs are provided with funds for their management, we might assume that bracken control will occur.

So we may accept that bracken should be controlled. How might we do this?

Ways of controlling bracken

  1. Eradicate it (kill it so thoroughly that other plants can grow) See below for more detail, but: (i) spraying with Asulam, perhaps from the air, requires follow-up perhaps annually for a period of maybe 3 years. (ii) Cutting needs to be done 3 or 4 times within the growing season and for at least 3 years. In both cases you’d know when it had succeeded, since other stuff would be growing, but you’d not be sure until the bracken was no longer appearing, so some continued surveillance is required, probably on foot. Maybe one solution is to make it a notifiable weed? It is probably not rampant enough to so classify.

  1. Use it (find things that will eat it, find uses for the plant). Wikipedia entry good here.  Eat it. The curled emergent fronds, fiddle heads are edible. Perhaps we should? The RHS says bracken contains carcinogens linked to cancers of oesophagus and stomach, but the particular poison is both water-soluble and is destroyed in heat and alkaline conditions, so proves safe enough if treated sensibly. Translation, edible if for example, it is cooked.

  1. Control policies. Pakeman, Le Duc and Marrs (source, 1999) point out that there is a long history of bracken control. They tell us that there are two conventional control methods, Asulam2 and cutting3; they also say that control attempts fail because there is insufficient after-care, as above.

Speaking as a user of the hills, I am aware that spreads of bracken are slow going until one has found a path. I am told that one can be cut by bracken, but have never experienced that. I am not slow in the hills, but accept that perhaps I do slow down just enough in such high growth. On the other hand, bracken grows on dry ground, so it is relatively reliable footing. Paths tend to be sheep width so they make fair going for humans. off such routes the going is very slow; when the growth is head height, it is very easy to be completely thwarted (and I often fall over). I am aware that I stay away from bracken in the high summer, but I have not been until writing this, conscious of reasons why. I suppose given a choice between tramping through heather and ferns at the same time of year, I’d look to walk along the interface between the two, which is where paths will often be found. I frequently remind myself that walking as much as 30º off line only adds 15% to the distance, and that the speed gain in ‘aiming off’ along footway that is better than the direct route, so the net effect is a positive gain. So tracking me when in the hills and off any recognised map-marked path would often show me to be around 15º offline and using some animal track. that’s because i’m looking where i’m going and trying to pick the optimum route in terms of distance gained for effort applied. Further, faster.

It just so happened that, the day before writing this, I had indeed been in the Lakes and off any path for four consecutive hours, discovering lots of bracken and operating as described above. Bracken is preferred underfoot to tussock grass; heather is preferred while only small, but even full height heather is preferred over full height bracken.

My conclusions:

  1. Bracken control seems like a jolly good idea. It displaces other plants we would prefer to have. We are unlikely to eradicate it.
  2. Aerial spraying continues to be an issue for other users of land. I suggest we need to move from nanny state to one of caveat emptor. It would be far simpler to find out the state of the spraying on the moor, as one would for, say, the tide at the coast. Sensible application of notices in carparks, raising awareness of moorland issues seems an obvious move.
  3. Any fuss about Asulam treatment being possibly carcinogenic is countered by the plant itself being proven to be so, where we have no evidence either way about the spores’ effect upon humans, but it is more nearly proven than that Asulam is one.
  4. The reasons for Asulam being removed for EU approval were not found by me. The ex-pupil referred to below (thanks, Adam) did one of his magic searches and came up with this reference, which explains that when Asulam was used on spinach there were different issues identified that require further consideration before the residue definition for consumer risk assessment, and consumer risk assessment could be concluded. .... Two data gaps were identified in the ecotoxicology section. The long-term risk to birds and the risk to non-target terrestrial plants were identified as critical areas of concerns. I think this means that the submission for acceptability was insufficient, which is not the same as saying the chemical is unsafe. Do tell me if you think it means something different. Oh, and spinach is not bracken.
  5. We ought to explore further the possible modern uses of bracken - i.e to experiment towards farming it. I suspect that the cost of moving any crop works against its possible usefulness, especially one that grows in inaccessible places.
  6. There are continuing issues with crop spraying; we have recommended procedures, but they are hard to follow (to comply with. Just a small amount of wind causes unwelcome spread, which makes living in the countryside uncomfortable. been there, done that. So, even on the large uncultivated areas for which we might like to spray Asulam upon bracken, it would be a good idea to be not-there on a spraying day. Not because Asulam is inherently dangerous, but because spraying is generally a bad way to ingest what are, fundamentally, poisons, even if not especially poisonous to humans.
  7. Yet again, social media exposes belief rather than fact, even among those who would like to think of themselves as informed. That may be because for what we might call the echo-chamber effect. We need a culture in which people challenge each other to justify statements and to supply their evidence when making such. Indeed the original Facebook page I was looking at caused response from me because a past pupil was doing exactly that; not only was he pointing out that claiming ‘something was up on the site but it has since vanished’ was not helpful, he explained how one could record such a matter and what he had discovered with a slightly more sophisticated search routine5.

Thus he fulfilled his own stricture. I like it. Thanks again, Adam.

DJS 20170621

top pic; do you care?

I apply a policy of not using full names. That is partly because I don’t have permission, partly because I have long felt that pushing someone else’s name ‘out there’ is wrong even with permission and partly because it is bad enough if i get things wrong, but having someone else’s name associated with my screw-ups is not fair. I didn’t say those were equal measures.

The Facebook group that prompted this essay has taken no evident notice of the rare voices of reason. That is very sad on several counts. One of those is that the echo-chamber effect perpetuates whatever misconceptions are held, in a sense driving the group as a whole into (group) recognition of some things which are not true (or at best partly true). Worse, it seems to collect such misconceptions and exaggerate them – they seem to become more extreme rather than less so. I deem this a social medium failure. A wider issue, raised at the head of this piece, is that we have not collectively gained any great tendency to test assumptions, nor to attempt to check ‘facts’. It took a while, but it was do-able. By reporting where I found stuff, you could go read it for yourself far more quickly and test those sources against others. Reach your own (different) conclusion, even.  I hope I am receptive to disagreement in interpretation of what I read; I hope I express myself sufficiently clearly to allow you to reach your own conclusions and, specifically, to disagree with me while still wanting to read content. I do not think I have any particular axe to grind, but for the one attempting to persuade people to think for themselves.

Which is entirely different from those wishing to move public opinion to some target space. At least, I hope that it is.  Adam observed that this may well become worse with the next iteration of social media platforms; I guess he anticipates that we will find it even easier to populate groups of similar opinions to our own, each such group riddled with fractional truth. If so, it is going to become rapidly more difficult to fight against established (merely by repetition) ideas with anything containing properly supported evidence. Thus we may well see that the idiocies of Brexit and Trump as POTUS (my opinion) are just the beginning of a wider move towards the dark Age I was writing about in essays 225 and 226.






1 I have been confusing Lyme disease with Weil’s disease. Silly me.

However, bracken litter is an ideal habitat for sheep ticks, and in addition to the impact on livestock and birds, ticks can carry diseases that infect humans, and can even prove fatal. Bracken control is important to minimise the threat to walkers.




2 Asulam An apparently magical herbicide, which attacks bracken while not affecting adjacent plants in the same environment. Declared ‘not approved’ within the EU in 2011, this has had the effect of causing lots of outrage at its continued use in the UK. The reasoning for the retraction of approval by the EU is difficult to comprehend. I suspect that the product was used for things not to do with bracken and as a result caused damage to edible foodstuffs, but I failed to find any evidence.  The reasoning for use in Britain for suppression of bracken is by comparison quite clear; it works specifically and equally specifically does no apparent or recorded damage to adjacent plant life. Whether that means we should avoid human traffic through treated bracken for a while was less easy to discover.

The vegetation of 117 bracken-dominated sites that had been sprayed with asulam from the air over a wide range of dates was recorded. There is a high variability in initial efficacy and sites displayed considerable differences in regeneration in the years following treatment. Sites treated more than 10 years previously all showed good control of bracken. The absence of sites where bracken has regenerated completely was attributed to either respraying at a later date or the poor records kept of previous unsuccessful control measures. There was also a high degree of variation in the amount and type of herbaceous vegetation present below untreated bracken. The data presented suggest that aerial spraying of bracken with asulam can be a long-term and cost-effective control method. However, in the light of experimental results from other studies, the success of an individual operation is critically dependent on the initial efficacy of treatment, the initial floristic composition (if any) and suitable follow-up management. Source

Bracken Control has a site explaining some of the situation. Asulam should be applied between July 1st and mid-September; it is often applied by aerial spraying. It is (source) only cost-effective way of tackling large-scale areas of bracken in difficult terrain. ... Its bracken specific property allows Asulam to be applied as an overall spray with manageable risk to non-target species. The use of a helicopter, and potentially a drone, to apply Asulam opens up the opportunity to apply it efficiently to large areas of steep or difficult terrain in remote areas, which it is not possible to reach by other means.

Follow-up, or after-care as I called it earlier, means going on foot to spray fronds by hand, using Asulam at low concentrations (1:100). Doing this mechanically uses too much water, causing run-off and problems elsewhere, specifically where the bracken is not. As ever, the level of recorded research is poor. One wonders (oh yes I do!) the extent to which such reporting is there to cause grants for the work of measurement when the same money might (also) attack the problem. Indeed, one wonders the extent to which tree-huggers in general have vested interests in generating work for themselves. A pity, if true, since in general the research continues to not deal with the problem.

Is Asulam carcinogenic, as I found claimed on this site?  See here, which says  unlikely to be an acute hazaard, but against cancer info, says ‘not listed’; to me that means case unproven either way; indeed ‘possible’ is a fair label.  But then exactly the same label applies to walking through endless ferns at the same time of year as spraying would occur4 It seems likely that all chemical spraying is something we should do with due care and attention to other users of the land. if we were to post information about when spraying was to occur, we might then modify our other plans for use of the land until the spraying was complete, without needing to spend huge sums on physical notices. in a sense, move the responsibility for the safety from the sprayer to the other users of the land, having established that spraying takes place in a particular window and when the weather is suitable. A sort of caveat emptor state; a long way from a nanny state.

3 Cutting   site

The BCG is encouraging new approaches to bracken control:
o The use of drones is being considered;
o Cutting to produce garden compost;
o Cutting to extract bioethanol; and
o Cutting to produce ‘braquettes’ for burning on a wood-burning stove.

Experiments on the North York Moors have shown that cutting cannot achieve clearance unless it is done at least 3 or 4 times per growing season, to a very low level below the height of surrounding vegetation and for at least 3 or 4 years successively. Labour costs make this impracticable in many situations. It is not possible to cut bracken with machinery low enough without risking damage to other vegetation and/or causing damage to surface peat that can lead to an erosion risk. Furthermore, mechanical cutting may cause damage to known and unknown archaeological interest preserved in the peat.  source

Bracken does not well tolerate being trampled by livestock, so one control method is to mechanically damage the plants. That presupposes that the spore-rich atmosphere is safe for humans. There is a proven correlation showing that the carcinogenic compound in bracken, ptaquiloside or PTA, can leach from the plant into the water supply, which may explain an increase in the incidence of gastric and esophageal cancers in bracken-rich areas. I suggest then, that Bracken is as more nearly shown to be carcinogenic than Asulam, which does not say that one is more carcinogenic than the other.

4  Bracken is shown to be a carcinogen when ingested by animals. wiki entry. The spores have also been implicated as a carcinogen.

5 site:<URL> <search string>     e.g. site:scoins.net idiot      had 18 hits when I tried it.

Writing was interrupted by a “Shit! the Washing!” moment. Meaning: drying, getting wet in the rain shower. Such is Stockport.

© David Scoins 2017