Is Glyphosate the best solution for amenity weed control?
A 2021 study to investigate alternative approaches to weed control in urban areas has concluded that glyphosate is "the most effective and sustainable weed control method currently available".
These weed control trials were designed and managed by an independent research consultancy (Advanced Invasives Ltd., Dr Dan Jones) and conducted by PCA member Complete Weed Control and Cardiff City Council, the results of which were published last week (12th January).
The PCA was pleased to offer a prelude to this study at the recent International Invasive Weed Conference and Technical Manager Peter Fitzsimons welcomes the opportunity to discuss the final report/results in more detail....
Why were these trials conducted?
Discussions about the herbicide glyphosate are necessary and useful. As a society we need to be sure that the products and processes we use to manage weeds, whether in food production, forestry or in urban settings, are safe and effective and indeed there are a raft of laws and Regulations which aim to give the public confidence that this is indeed achieveable. Nevertheless, the use of chemicals, particularly in close proximity to people’s homes or in public spaces, is an emotive subject so there is a continuous debate about three things: are the products safe (to humans and the environment), are they necessary and are they effective (in the context of alternative strategies)?
The Cardiff Council study address almost all of these issues and presents a life cycle analysis concluding that glyphosate, when used to manage urban weeds (i.e. those affecting predominantly paths, paved surfaces and roads), is sustainable and is consistent with the Council’s Biodiversity and energy policies.
The study report is 75 pages long so if you want all the details please follow this link to the Cardiff Environmental Scrutiny Council meeting where all the documents can be found (plus a video). But here are some points from the Councils’ own summary (with PCA comment):
Results of Alternative Weed Control Trial
The independent trial assessed three different approaches to managing plant growth on Cardiff's highways and pavements and concluded that glyphosate is "the most effective and sustainable weed control method currently available".
The viability of two ‘eco-friendly' alternatives (Hot Foam and Acetic acid) to the glyphosate-based approach were assessed but glyphosate was found to have a smaller overall environmental footprint than either of the two alternatives. Glyphosate was also the least expensive product tested and ranked highest for customer satisfaction (least complaints).
In the report Dr Dan Jones says: "What we found was that not only is glyphosate the most efficient and effective way of controlling weeds, but once you look at the full life cycle of the product, factoring in things like the amount of fuel and water-used, it is also the least damaging to the environment. The glyphosate-based approach to weed control currently used by the council is the most sustainable method of weed control currently available in the UK."
A Cardiff Council spokesperson said: "The Council has a duty of care to keep Cardiff's streets and pavements free from trip-hazards and is also determined to achieve its One Planet Cardiff goals, reduce carbon emissions and protect the environment. The results of the independent trial suggest that the best way of doing that is to continue with our existing approach to weed control, while continuing the work that has already seen the amount of glyphosate applied in Cardiff reduced by 80% compared to previous application methods."
This last point is an important one. Apart from the global conversations about glyphosate safety, Cardiff Council or any other organisation are legally obliged to ensure that all weed control activities are conducted under the principles of Integrated Weed Management. This means that non-chemical methods where appropriate should be used alongside herbicides and that herbicide use (volumes, frequency) should be the minimum consistent with justified weed management objectives. As they say, a lot has been achieved over recent years e.g. by the deployment of new application technology but this study was needed to ensure they had a sound basis for the continued use of glyphosate as part of an Integrated approach (as oppose to an outright ban on its use).
How important is this report for Invasive Weed control?
The herbicide Glyphosate is a key component of most invasive weed control strategies, so any study which sheds some light on its sustainability credentials compared with alternative so-called 'eco' strategies is not just useful, but fundamental to its continued use/specification under current pesticide guidelines - as reflected in Defra’s Code of Practice and the Plant protection Products (Sustainable Use) Regulations 2012.
This study addressed the need for weed control in urban areas on the grounds of aesthetics, safety and accessibility and their potential to damage assets (e.g., buddleia). A similar justification can be made for non-native invasives; that is, they are an environmental hazard (especially in ‘wild spaces’) and in urban settings can cause damage and/or other negative amenity impacts (limitations on land use).
As above, the cost and practical limitations of 'green' alternatives limit their suitability, so glyphosate-based herbicide control programmes are key to providing, say, homeowners with an affordable solution to their needs and enable us on a National basis to put a brake on the environmental damage caused by Japanese knotweed and other species such as Bamboo, Giant Hogweed, Himalayan balsam etc.
Finally, we should say that this study was restricted in its scope – not all chemical or non-chemical approaches are applicable in pavement weed management. Other approaches to weed control are used for invasive weed management; electricity, physical removal, excavation and ‘tarping’. These are frequently put forward as ‘green’ alternatives to the use of selected/targeted herbicide application for e.g., Japanese knotweed control.
However, it seems likely that if the same analysis were carried out as above in Cardiff (short and long term effectiveness, energy and resource inputs, habitat disruption, £ cost), it is likely the green credentials claimed for these methods (as recently as this week in The Telegraph!) would need to be revised. This is NOT to say a chemical approach is always best but this Cardiff study does make it clear that lazy assumptions that non-chemical approaches, or simply avoiding the use of glyphosate, provides better outcomes, or ones which are more sustainable, are necessarily true or helpful from a client or environmental perspective.