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Scientists comment on an analysis of UK pesticide usage data.
Dr Wayne Carter, Associate Professor at the University of Nottingham, said:
“The increased use of glyphosate poses a potential health concern for individuals who are extensively exposed. As with any other pesticide, glyphosate can be toxic, depending upon the level of exposure, either acutely or potentially chronically. The public may be exposed to glyphosate via food or by using certain weedkillers, but some people may be more responsive to the toxic effects than others and the level/duration of exposure is also crucial – the human health impact of everyday exposure for most people in the UK is very difficult to determine. The increased usage of glyphosate should be paralleled with increased biomonitoring of human exposure to ensure that this stays within the suggested safety limits.”
Dr Helen Metcalfe, Agricultural Ecologist, Rothamsted Research, said:
“Glyphosate is the world’s most widely used herbicide, and one of the most contested. The debate spans science, policy, and public opinion. Glyphosate use in the UK has increased dramatically in recent times and the recent confirmation of glyphosate resistance in a UK arable weed population served as a serious warning sign. When resistance evolves in a key herbicide, the tool can become ineffective.
“However, glyphosate remains one of the most important tools available to farmers, but we must remember it is only one component of a broader integrated weed management toolkit, and the priority must be to preserve its long-term efficacy.
“Minimum tillage systems (which minimise soil disturbance) help to preserve soil structure, build carbon, and reduce erosion. They are central to regenerative and conservation agriculture. But removing tillage requires an alternative means of weed control, and glyphosate currently provides the most effective substitute for the mechanical destruction of weed seedlings that tillage achieves. It is for this reason that glyphosate sits at the heart of the farming systems best positioned to deliver soil health benefits at scale.
“The appropriate response is responsible stewardship: reducing overall glyphosate use to essential use cases, integrating glyphosate within broader rotation-based weed management strategies, and adhering to best practice guidelines on resistance management, human health, and environmental safety.“
Prof Toby Bruce, Professor of Insect Ecology, Keele University, said:
“Glyphosate has extremely low human toxicity but is also extremely effective at killing a wide range of plants. It is a useful herbicide that facilitates adoption of conservation agriculture, where cover crops can be grown to protect the soil, and then sprayed off later with glyphosate, to allow preparation of the land for the subsequent food crop being drilled.
“Glyphosate has been demonised by pressure groups, perhaps because it is the herbicide that is used together with GM herbicide resistant crops. The anti-synthetic pesticide pressure groups often also dislike GM crops, as an “a priori” anti-technology stance regardless of evidence.”
References:
https://dceg.cancer.gov/research/who-we-study/cohorts/agricultural-health-study
Mr John Cussans, Weed Science Principal Consultant, ADAS, said:
“It might seem nit-picking but I think it’s worth pointing out that the glyphosate used on farmland isn’t “being applied to UK crops” – this is an important distinction since it differentiates glyphosate use in the UK, and across Europe, from other places in the world where glyphosate tolerant crops are being deployed. Quite often a google search for “glyphosate in agriculture” comes back with information from parts of the world where (GM) glyphosate tolerant crops have been adopted and some of this can be mis-leading so it’s important to look at glyphosate in a UK (and European) context.
“With conventional (non-glyphosate tolerant crops) glyphosate is a total weed control herbicide. It is actually, currently, our only total non-selective weed control herbicide which makes it an important pesticide for conventional (non-organic) agriculture – glyphosate controls all plants it is applied to and hence cannot be sprayed onto a growing crop – it is used in the UK in three ways; 1. prior to planting the crop (or a small amount is applied just after planting but before the crop seed has germinated) in order to clear the fields of whatever vegetation is present, 2. a smaller amount is used to stop the crop (and any weeds present) from growing once it is mature and aid harvest .. so called crop desiccation and 3. A really very small quantity in some specific crops is applied using the height difference between crops and weeds at maturity in an attempt to prevent weed seed return- this is often referred to as weed wiping because of the equipment most often used to apply glyphosate in this context.
“There’s no doubt glyphosate use on farmland has increased dramatically over this period in reality probably not quiteas much as these data imply since over time we have got better at recording and capturing it’s use – glyphosate use is a tricky one in pesticide surveys since it is often used between crops, as it were, and when surveys are carried out by crops or crop-type it was often missed. Given the focus on glyphosate currently we can be pretty confident that it’s use is being captured in the statistics effectively now. The increase is in part driven by a lack of direct (chemical) alternatives – farmers used to be able to apply other non-selective herbicides; paraquat, diquat, glufosinate but these are no longer available. The increase is also driven practically on-farm by an increased requirement as a result of other elements of public policy. Public policy has focused on reducing cultivation and diversifying cropping both of these trends increase requirement for glyphosate applications. As Martin Line’s statement implies a big driver is reduced cultivation .. You can grow crops right now with no glyphsoate but you would need to get the same level of non-selective weed control largely from cultivation/mechanical weeding, as Martin puts it, “excessive cultivation systems that lead to poor outcomes for nature and our soils” and this is something we want to avoid if we can. I think, in reality, the story around glyphosate use is nuanced; glyphosate use facilitates other practices in agriculture which are incredibly positive, adoption of ‘conservation’ or ‘regenerative’ agriculture brings reducing physical soil movement and increasing the diversity of crops while maintaining ground cover for more of the year.
“Away from Farmland considering the use of glyphosate for weed control in built-up areas, roadsides, parks, playgrounds often called ‘amenity use’ it’s absolutely true that glyphosate usage data is patchy and hard to interpret. Amenity weed control, including a lot of local authorities, does use a lot of glyphosate to keep playgrounds, paths, pavements and road edges clear. There have been studies, including some large practical ones, evaluating alternatives in amenity settigns (there’s a nice summary here https://www.bcpc.org/wp-content/uploads/2017/11/Weeds-2017-Mason.pdf of a big study in Thanet there was also a big study https://www.cardiffnewsroom.co.uk/releases/c25/30579.html in cardiff). For local authorities, who have been put under so much pressure during and after ‘austerity’, it comes down to cost – there are currently alternatives but they appear to be very much more expensive and hence difficult for councils to adopt without big increasing in their budget. As an aside since the world is litigious councils seem concerned in particular about weeds causing trips and falls, for example paving slabs lifting or visibiliy from vehicles being obstructed, so it seems that they are not minded to reduced level of weed control.
“It’s hard to argue with the point Martin Lines makes because research is very much needed into optimisation of glyphosate use, exploring direct alternatives for total non-selective weed control technologies (these at the moment we are beginning to see but they are in their infancy) AND on other cultural and non-chemical weed management tools right around the cropping system which reduce the pressure on glyphosate from a weed management point of view. The impetus for prioritising this research is not, from my perspective, concerns about the risk of glyphosate use to human health but rather on reducing our increasing reliance on this herbicide for overall weed management .. Increasing reliance on glyphosate has I would argue been a key driver for the evolution of glyphosate resistance in the UK. We do want the positive benefits which conservation and regenerative agriculture can provide but at the same time we do not want to become over reliant on a single herbicide to deliver those benefits.
“Basically as with so much else in life it’s never black and white – there are trade offs all over – reduced cultivation and glyphosate use / cost-effectiveness and glyphosate use.”
Declared interests
Dr Wayne Carter: “I can confirm that there are no conflicts of interest associated with my comments.”
Dr Helen Metcalfe: “HMs work is primarily funded by BBSRC and NERC. She works on one industry-linked research project funded by CropLife Europe to define off-crop plant communities. This work informs agrochemical industry risk assessment of plant protection products.”
Prof Toby Bruce:
“BBSRC project BB/M011542/2, “Lure-and-kill technology to manage beetle pests (Sitona lineatus and Bruchus rufimanus) of field beans and peas” (2014 -2018), had a small proportion of industry funding from the chemical company BASF (Less than 5% of the cost of the project).
“BBSRC project BB/X011844/1, “Crop protection against aphids with plant defence activators” (2023) was 10 % funded by an agronomy company, Agrii but they are a distributor of crop protection products, not manufacturer.”
Mr John Cussans: “I am a full-time employee of ADAS and do not receive personal income from any other sources. I do not have any personal shareholdings in companies involved in crop protection or agricultural production.
ADAS is an independent consultancy and R&D provider in agricultural and environmental land management (see https://adas.co.uk/about/) and is part of the larger RSK group (see https://rskgroup.com/) which is a global provider of environmental, engineering and technical business services. My work in ADAS is on the development and promotion of integrated weed management including monitoring and understanding the development of herbicide resistance. This work is funded from a number of competitive sources including the government (e.g. UKRI, DEFRA and Natural England) and it’s agricultural levy board (AHDB), private companies with interests in best practice in agriculture such as water companies, companies with providing products or services directly to farmers and their advisors and manufacturers of crop protection products.
Specifically with regard to manufacturers of herbicides containing the glyphosate active (relevant to this briefing); ADAS has in the past and does currently have some contracts to provide R&D (field and glasshouse efficacy testing and weed management experiments) and support knowledge exchange (farmer meetings and other events) for a number of these companies including but not exclusively Bayer Crop Science (who are the most significant company with regards to glyphosate products in the UK). These contracts are on a range of crop protection and weed management (chemical and non-chemical) topics with a very small number of projects, perhaps one or two a year, involving products containing glyphosate directly.
Alongside employment for ADAS I do have some unpaid roles promoting and supporting weed science in the UK; I am a technical member of the Association of Independent Crop Consultants; I sit on the Weed Resistance Action Group (WRAG) and I am a members of the BCPC expert working group on weeds.”