NIAB - National Institute of Agricultural Botany

Orson's Oracle

Ipomoea and Colonel Gadaffi

Posted on 06/10/2017 by Jim Orson


We have just returned from a holiday in the very South of France, where the Pyrenees meet the sea. On one strenuous walk, a loop of around 20  km, we climbed for around 3 hours. Initially there were vineyards, but then trees and then just scrub. At the  highest point of the vineyards we saw a lot of ipomoea growing up wire fences. The ipomoea genus is part of the Convolvulaceae family and have coloured flowers rather than the white flower of our commonly occurring field bindweed (Convolvulus arvensis), pictured above. The ipomoea was in full flower and very beautiful.

It is amazing how simple observations can lead to associated memories. I have only been asked once on how to control ipomoea, in this particular case morning glory (Ipomoea purpurea) which is pictured at the end of this paragraph. It was on the morning of 15th April 1986. You may be impressed that I could remember the date or you may think I keep meticulous records of the inquiries I receive: not a bit of it. It was a Breckland farmer who made the inquiry. He also told me, well before the news broke, that US Air Force fighter bombers and their re-fuelling aircraft had that morning taken off from nearby Lakenheath and Mildenhall to bomb Libya. I have just checked the date of the raid to inform you precisely when the inquiry was made.

Jim orson blog 205

I had become accustomed to inquiries from the Breck on the control of exotic weeds. Vegetable crops are widely grown on these sandy soils in East Anglia. In those days imported seed was regularly used. This seed used to include the occasional ‘stranger’. The most common introduction was barnyard grass (with the wonderful scientific name Echinochloa crus-galli) in carrot seed. The ipomoea inquiry was a little different as in the previous year it had mysteriously appeared growing up one of the farmer’s isolated tall wire fences and had survived the winter. Later, I found out that its seed contains psychedelic chemicals which may have been the reason for its sudden appearance along a significant length of fence line. I assume the glyphosate applied at the time of the appearance of the first flowers saw an end to it.

None of these occasional introductions resulted in the establishment of field infestations in the Brecklands. Thankfully, they were a novelty rather than a threat.

In fact, I cannot think of a recently introduced annual weed causing issues in arable crops in the UK. We thought that awned canary-grass, that became a field problem in some limited areas in the early 1980s, was a new introduction but in fact it was recorded in field crops a century earlier. More recently, more infestations of rat’s tail fescue (Vulpia myuros) have occurred in no-tilled crops but it appears that it too has been around in our crops for a long time. NIAB TAG is currently doing some research on the control of this weed.

However, over the centuries there have been significant introductions of plants that have become major arable weeds in this country. The most significant being black-grass, wild oats, rye-grass and common poppy. Botanic databases have three categories of plant introductions; native, archaeophytes and neophytes. For this blog I have used the database of the Biological Records Centre. 

Native species were around when cultivations and crop production were first practised in Britain. These include chickweed, knotgrass, redshank, annual meadow-grass, rough meadow-grass, Yorkshire fog and meadow brome. Anyone familiar with the novel will be happy to note that the scarlet pimpernel is also a native species! It is interesting that the native annual broad-leaved weed species tend to be those that commonly occur in current spring-sown crops.

Archaeophytes are those species introduced in “ancient” times when some limited international trade first started. These include black-grass (a native of Eurasia), rat’s tail fescue, spring wild oat, black-bindweed, common poppy, scentless mayweed, common fumitory, ivy-leaved speedwell and barren (sterile) brome.

Neophytes are those considered to have arrived in Britain with the opening up of inter-continental trade. The threshold seems to be since 1492 when Christopher Columbus arrived in the New World. These species include awned canary-grass, winter wild oat, common field-speedwell and Italian rye-grass.

The problems with introduced weeds are not restricted to arable agriculture. The perennial neophytes, Japanese knotweed, giant hogweed, Himalayan balsam and rhododendron (ponticum) can cause real problems, so much so that it is illegal to plant them in the wild or to cause them to grow in the wild.

Perhaps the country whose land is most affected by non-native weed species is New Zealand. They currently face the challenge of the very recent introduction of velvet leaf, a really nasty annual arable broad-leaved weed. Whenever I spoke on weed control in NZ I was jibed about Britain sending them all their weeds. I had to explain that this was not true because it was their ancestors who brought the weeds with them. Britain is innocent of all charges!?

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The precautionary principle

Posted on 22/09/2017 by Jim Orson

The adoption in the current EU Pesticide Regulation EC 1107/2009 of what is claimed to be the precautionary principle could be a reason for the withdrawal from the market of pesticides that might otherwise be approved. What is the precautionary principle and what is its role in EC 1107/2009?

There is continuing confusion over the precautionary principle because many of the definitions I have read disagree as to whether or not it includes risk assessment. Some suggest that the precautionary principle is purely risk prevention (avoiding the possibility of harm) and does not include risk assessment (quantifying the risk of harm). Other definitions include both risk prevention and risk assessment. Hence the general understanding of the term ‘the precautionary principle’ is a real mess and open to exploitation by those who are opposed to a particular activity.

Rather bizarrely the European Commission has not got a legal definition of the precautionary principle despite its reliance on it in its pesticide legislation. The European Commission says in a paper on the subject “it would be wrong to conclude that the absence of a definition has to lead to legal uncertainty. The Community authorities' practical experience with the precautionary principle and its judicial review make it possible to get an ever-better handle on the precautionary principle”. This statement seems to assume that a legal definition is not yet possible.

In the USA there is a legal definition “when an activity causes some threat or harm to the public or the environment, general precautionary measures should be taken. When a scientific investigation proves that there is a possible risk in doing some activity, then this principle should be applied”. I interpret this to mean that, in this case, risk assessment is part of the precautionary principle. Risk assessment of pesticides involves quantifying the known risks in order to prevent harm to humans and the environment. However, it is not always possible to quantify all the risks and so, in the meantime, it can be argued that there may be a role for risk prevention.

Prior to the EC 1107/2009 the registration of pesticides was based on risk assessment. Safety factors for the impact on human health were (and still are) at least 100 fold, which I would argue is a very precautionary approach to risk assessment. However, EC 1107/2009 introduced the risk prevention approach of hazard cut-offs. Those active substances that are deemed to be carcinogenic, mutagenic, a reproductive toxicant ("CMR"), a persistent organic pollutant ("POP"), a persistent bio-accumulative toxic substance ("PBT") or a very persistent and very bio-accumulative substance ("vPvB") will not be approved unless there is negligible exposure in which case they may be approved under restricted conditions. Reassuringly, this sounds as if some form of risk assessment can be carried out rather than have an outright ban based on risk prevention.

These hazards were taken into account in the risk assessments under previous registration regime and surveys of UK sprayer operators, i.e. those most exposed to pesticides, suggest that this approach was robust. Hence, in this case, hazard cut-offs, deemed to be necessary under the precautionary principle, seem to be both unnecessary and also do not meet the understanding that such an approach is necessary only when a reliable risk assessment cannot be carried out.

Then there is the issue of endocrine disruptors i.e. those chemicals that can affect the hormone systems of humans and organisms in the wider environment. As many will know, the concern is that including endocrine disruption in the EU pesticide legislation could potentially remove a raft of key pesticides, including some or all of the triazole fungicides.

It is claimed that endocrine disruption could cause significant human health and environmental impacts. Strictly speaking, the current EU legislation for plant protection products does not include endocrine disruption in the hazard cut-offs. However, and similar to the listed hazard cut-off, it says that active substances which are endocrine disruptors will not be approved, unless there is negligible exposure. In this case they may be approved under restricted conditions. This again sounds as if some form of risk assessment can be carried out in certain circumstances. Unfortunately the mode of action of some insecticides is the disruption of the target insect’s endocrine system. Fortunately, it is acknowledged that some insecticides which have endocrine activity that affects target arthropods (e.g. insects) do not affect vertebrates. These insecticides will be subjected to a specific risk assessment and approved only if there are no unacceptable effects on non-target organisms. Last week the EU ministers adopted the European Commission’s draft criteria for endocrine disruptors in plant protection products. These will replace the interim criteria that have been used over the last two or three years.

It seems to me that the hazard cut-offs in the current EU Pesticide Regulations, which do not include endocrine disruption, are not necessary because the risks can be quantified. Hence, a risk assessment approach rather than risk prevention is appropriate. I am very much not alone in this belief. A review of EC 1107/2009 is being carried out and could result in changes over time. However, Brexit means that pesticide legislation specific to the UK may or may not be just around the corner. The first day of the BCPC Brighton Congress on pesticide regulation is on 31st October. The introductory speaker is George Eustice, Minister of State Defra offering the Government’s latest thinking on the outlook for the industry. Details of the whole conference can be found on Those wishing to attend just the first morning (and lunch) at a discounted rate should email or ring Julian Westaway on 07710 556382.

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Wheat seed rates

Posted on 08/09/2017 by Jim Orson

In my most recent blog I suggested that the industry needs more research on stubble management for black-grass control. However, that comes with the caveat that such research will illuminate rather than confuse. There has been an example of research causing confusion on another current issue. At the end of the last century the industry was content that seed rates for winter wheat was a done deal. NIAB TAG had been doing research for years and had achieved, what we thought, robust guidelines.

Then in 2000, AHDB published a project report on winter wheat seed rates. It suggested that the typical recommended optimum plant numbers at the time, including those recommended by NIAB TAG, were far, far too high and huge cost savings could be made on seed. Understandably NIAB TAG staff sat down and read the AHDB report very carefully to see if we had missed a trick.

It soon became clear that we had misgivings about the report. First of all the choice of treatments broke the common sense rule I was taught in my first statistics lecture at University. The key message from the lecturer on choice of treatments was to ensure that there should be adequate coverage of the likely or assumed optimum values: it is a common sense approach to help ensure a clearer identification of the actual optimum. He was keen on common sense throughout the course of lectures. He emphasised that there is always the danger that getting too pre-occupied with statistical techniques can cause a drift away from reality.

The seed rates tested in the AHDB project were 20, 40, 80, 160, 320 and 640 seeds/m2. Hence, there were no treatments between 160 and 320 seeds/m2 (roughly 80 and 160 kg/ha) and also between 320 and 640 seeds/m2 (roughly 160 and 320 kg/ha). I was told that this was a true scientific approach but having poor coverage of the typical recommended seed rates of the day worried me. The average results of the project are shown in the first graph below. The horizontal axis shows the plant/m2 established after the increasing seed rates tested and the vertical axis shows the resulting yields.

Another concern was that using what was said to be the best line fit, known in the trade as a linear plus exponential function, resulted in a straight line between the 160 seeds/m2 and 640 seeds/m2 treatments, i.e. the seed rates producing the three highest plant populations in the graph below. This worried me even more because the straight line meant that the economic optimum seed rate had to be below 160 seeds/m2, or if it sloped upwards sufficiently for the additional yield to more than pay for the additional seed, above 640 seeds/m2 (see the High Mowthorpe results in the second diagram below). Hence, in the analysis of these trials there could be no chance of an economic optimum seed rate lying between 160 and 640 seeds/m2 i.e. the seed rates commonly used at the time. Our review of the AHDB project report resulted in NIAB TAG continuing to recommend the optimum plant populations suggested by its own trials.

AHDB report

And so the years went by. Then in 2011 there was a Defra science report on artificially imposed slug damage and its likely impact on seed rates. The same seed rates were used as in the AHDB report. The results of the seed rate treatments were not published in the same way. As I said earlier, in the AHDB report the horizontal axis is plant population and in the Defra report it is seed rate (see graph below). This is unfortunate.

The statistical analysis of results was similar but not quite the same as that used in the AHDB report. On the whole it appears that the economic optimum seed rates, where ‘slug damage’was not imposed, were far higher than those implied in the AHDB report. There were 5 instances in 28 trials where the straight line inclined upwards sufficiently to have optimum seed rates above 640 seeds/m2 e.g. High Mowthorpe in the graph below. There were only three instances where optimum seed rates were between 320 and 640 seeds/m2. The Rosemaund line in the graph below had an optimum seed rate of 174 seed/m2. There was a huge variation in economic optimum seed rates between sites and years and no clear conclusion could be made from the results. The question has to be asked: was this due to natural variation or due to the choice of seed rate treatments and the analysis of the results? Again, I am very uncomfortable with the information provided.

DEFRA graph

I have said many times that being a slave to statistical approaches and ignoring common sense can create difficulties in interpreting results in order to produce reliable guidance for farmers. I am delighted that 50 years ago I learnt something from my statistics course at University that is and will remain very relevant! Another continuing relevance is that wheat is a very adaptable crop and plants/m2, within a reasonable range of the optimum appropriate to the date of drilling, will give about the same financial margins. This is just as well with the variation in establishment that can occur in practice.

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Stubble management: where is the research?

Posted on 24/08/2017 by Jim Orson

I would not blame anyone for being totally confused about how to treat stubbles this autumn in order to minimise black-grass in future crops. I have read three separate articles on this subject in the farming press over the last few weeks which have intended to inform us. Unhelpfully, there seem to be three approaches being simultaneously suggested, sometimes within the same article! Some contributors are suggesting leaving the stubble undisturbed and allowing the black-grass seed to emerge. Then there is the very opposite advice being proffered. The stubble needs to be cultivated as soon as possible in order to get the black-grass seed to chit.

The contributors to these articles suggest that glyphosate should be used on multiple occasions to kill off the emerged black-grass but perversely also suggest that the farmer must think about the possibility of glyphosate resistance. Using cultivations to kill off small emerged black-grass is not mentioned as a possibility, although I do accept glyphosate must be used immediately before or very soon after drilling.

The third school of thought is that ‘it all depends’. I am firmly in this camp because that is what the data suggest. NIAB TAG staff regularly read trial reports from throughout Northern Europe and analyse the published data. It is a cheap way of supplementing our research for our membership. Trials can often have specific objectives and the authors of the reports regularly do not glean all the messages from the data. It is through this means that we came across data that provide a strong steer on how best to treat stubbles to maximise black-grass seed loss. Please note the emphasis on seed losses rather than simplistically encouraging seeds to germinate; one conclusion of this broad reading is that maximising losses, both those that occur through germination and those which are less visible, should be the goal.

The conclusions are pretty straightforward. When the soil is tinder dry, as it was last year, it is best to leave the stubbles undisturbed in order to minimise black-grass emerging in the following crop. In such conditions more viable black-grass seeds are lost from undisturbed stubbles than when shallow cultivations are adopted. This may be because the undisturbed soil surface structure seems to result in more black-grass seed germination in the stubble in dry conditions. It is also obviously the case that there are some natural losses from the soil surface. Shallow cultivations straight after harvest are more likely to provide an environment for seed survival in very dry conditions.

Around 15 years ago The Morley Agricultural Foundation funded a PhD on seed losses of different grass weed species from the soil surface. The conclusions suggest that nearly all seed from the major grass weed species are lost from the soil surface in the autumn and over-winter but some may be taken into the surface layers of the soil by earthworms. This study may, I emphasise may, have found the first evidence that birds predate black-grass seed from the soil surface during the winter.

The higher rate of black-grass seed losses in undisturbed stubble in very dry conditions rather goes against those who subscribe to the assertion that non-soil disturbance results in less black-grass germination than when the soil surface is cultivated. I have to stress that this is more relevant to spring sowing when some black-grass seeds need the stimulus of cultivation in order to germinate.

The opposite is true in moist or wet conditions. Incorporating the seed into a shallow seedbed straight after harvest results in less black-grass emerging in the following crop. This is hardly surprising when you think about it.

I have other gripes concerning these press articles! They mention weeds other than black-grass in their introductions and then, without any notice, specifically discuss black-grass. This only adds to the muddle.

Highlighting the present muddle means that I have to be absolutely clear;
• The effectiveness of different cultivation strategies post-harvest depends entirely on the context and, although there is work to be done in this area. The total losses of freshly shed seed seem to be maximised in dry conditions by leaving them undisturbed on the soil surface. In wetter conditions, however, some shallow, superficial cultivation immediately post-harvest to encourage black-grass seeds to germinate appears to be a more effective strategy.
• As an overall comment on the whole topic of post-harvest cultivations, there needs to be a focus on the totality of seed losses during this period and not just losses through germination.

My greatest gripe is that there is no publically available specific research on this issue. Unfortunately it is not headline stuff and does not promise to revolutionise arable production in one project. However, three years of NIAB TAG member-funded research suggests that a better understanding of this area of the biology of black-grass is critical to improving practical management on farm. That is what research is about: not the glamour of a quick fix promised breakthrough but of slowly and painstakingly producing better options for farmers. Instead, we have chaos and confusion.

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Why is life like a Dulux colour chart in monochrome?

Posted on 16/08/2017 by Andrew Watson

I am a simple man. I like things to be black and white. Day follows night, e=mc2 and Game of Thrones is on at 9pm on a Monday. A book titled 50 Shades of Grey sounds like a nightmare read to me.

Take Brexit. A black and white decision was made, like it or not, but we appear to be entering a decade of greyness. Whether hard or soft, I think it will definitely be a lemon Brexit - slightly firm on the outside, soft in the middle, leaves a sour taste in mouth and why-o-why would you to chew on it in the first place?

Agricultural regulations, which I’ve been involved with for 25 years, are the ultimate grey. The ‘Ministry’ (which I’m always reminded of when I see Gringotts Bank in Harry Potter), put out definitive black and white rules on a subject and this is what the farmer has to do.

But it’s not black and white. It’s like producing a Dulux colour chart in monochrome; endless shades of grey as the rules are interpreted at a practical level, by the experts, on farm.

Look at the Nitrate Vulnerable Zones (NVZ) rules which were so vague that the farm inspectors at that time, The Environment Agency, would publish periodic semi-practical interpretations to make the rules less grey. Like it or not, at least it provided more clarity - more black and whiteness. Then independent farm inspectors came along and interpreted the rules further, and often completely differently, on an individual farm. Back to grey again.

Pesticide rules are so “grey” that it can be difficult for a farmer or advisor to interpret them correctly. Which of the numerous buffer zones applies and where does the buffer start? What water volume or spray nozzle can I use? What are the definitive legal requirements for using this pesticide product?

As some of you know, I’ve spent over a year developing the definitive black and white database of pesticide products. ActivSmart, a NIAB Digital service launched at this year’s Cereals Event, puts all the grey pesticide rules and product data into one place in sharp, defined colour. It allows users to easily compare the defined attributes of similar pesticide products; with up to 26 black and white facts on each of the 2,300 plus approved products on the database. It provides clarity; from active ingredient to maximum total dose, from arthropod buffer zone requirements to a document library. ActivSmart is the perfect project for me as I get to replace shades of grey with black and white.

However, despite ActivSmart (with all modesty) being by far the most comprehensive, up-to-date but still simple, pesticide comparison tool, there is still a nagging greyness for a small percentage of the data.

Let me give you an example. In 2017, a new buffer was very quietly introduced by the UK Chemicals Regulation Division (CRD). This 5 or 10 m ‘non-target plant’ buffer around the outside of the field currently only affects five of the 41 products containing the active ingredient clomazone currently approved in the UK (yet more unnecessary greyness). However, CRD has published two authorisations for three of the five products. One authorisation has no new buffer but the other has the buffer clearly defined. In 2017, both these legal documents are valid. As a result the manufacturers can pick which authorisation to follow, and are not required to put the new buffer requirement on the product label in 2017 so they haven’t.

Clomazone is very toxic to many plant species and there is a history of legal disputes relating to drift damage onto neighbouring crops. It is one of very few products that must be applied as a coarse spray. I have concerns about how this grey area between CRD authorisations and product labels, both of which are legal documents, could potentially be viewed by a court of law should a serious legal dispute occur.

So, to finish, can I make a plea for more decisions to be made? Around the world and increasingly in the UK, no-one, even if they have the power to do so, wants to put their head above the parapet and say this is how it will be. Personally, it gets to the point that I almost don’t care what the black and white decision is but, please, please, make it and give us all a less grey world.

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