As a health and safety professional, I’m a fan of evidence-based approaches and I love a good scientific study (at this point, I’m sure you’re wondering how you can get me along to your next party!), so it was with interest that I read the recently released Cardiff Council study into the effectiveness of three different weed control methods for hard surface weed control.

The three methods – two herbicides: glyphosate and acetic acid, and a hot foam applicator which kills plants through the physical application of heat – were compared for sustainability in eighteen different categories, including petrol and diesel use, cost, water use and use of labour. The study also measured the effectiveness of the treatments using customer complaints and reports of weeds.

This intensive piece of research concluded that in terms of sustainability, cost and labour-intensiveness, as well as effectiveness, glyphosate was the most effective of the three options, concluding in the strongest terms that targeted use of glyphosate is “the most sustainable method of weed control currently available in the UK”.

So, what does this mean for integrated pest management (IPM) in the UK and for contractors working in amenity hard surface management – and particularly for local governments – and does it have major implications for invasive weed control?

First of all, what is IPM? Some people view IPM as “a holistic approach to pest management which uses all available methods” and others view it as “an approach which seeks to minimise pesticide use”. One widely accepted definition is that IPM strategy uses both pesticides and non-pesticidal methods in the most targeted and efficient way, with pesticide used as a last resort and pesticide use kept to a minimum.

Many people view IPM through a relatively narrow lens that “reduced pesticide use equals more sustainability” but as the wide variety of categories in the study illustrated, and as many people are increasingly aware, carbon footprints, water use and knock-on effects on biodiversity and pollinators are all valid parts of the sustainability equation. Given that the actual volumes and numbers of applications required to achieve control with alternative (contact) herbicides are higher, targeted glyphosate use may, counter-intuitively, reduce pesticide use.

What’s more, given the current economic outlook, cost is also an undeniable factor in choosing a treatment method – business sustainability and careful management of local authority fund is also a significant factor when drawing up, responding to and awarding tenders.

How this study might impact on other councils will be interesting to see. Many councils have bowed to public and lobby group pressure to switch to acetic acid or hot foam or other alternatives to glyphosate and may reconsider these decisions in light of the comprehensive research findings. Other local authorities have long been asking for in-depth evidence that they can use to back up their experience-based judgements that glyphosate provides the current most practical and cost-effective method of hard surface weed control.

Whether such studies or considered judgements are likely to be rendered irrelevant if the government pushes ahead with the withdrawal of EU legislation and repeals the Sustainable Use Directive remains to be seen, however, the amounts already invested in IPM technology, its status among trade associations and DEFRA as best-practice and its benefits in fields such as agriculture suggest that a sea change would not happen overnight.

Additional concerns are relevant in invasive weed management, where IPM also includes large-scale excavations, soil screening, burials and other physical remediation methods. The alternative methods considered in the Cardiff Council Study do not represent widespread practice in invasive weed management and further study would be relevant.

Acetic acid is not effective for long-term control of deep-rooted perennials such as Japanese knotweed, and though it may be effective at controlling annuals such as Himalayan balsam, alternative forms of control such as strimming and hand-pulling are available, though potentially more costly, labour-intensive or less sustainable by certain measures.

While there is some evidence that hot foam may be effective as a method of Japanese knotweed control, INNSA is aware of only limited trial use of this method in commercial Japanese knotweed control.

So, for INNSA, while this information is welcome, confirms the value of glyphosate as a tool for weed control and suggests that the retention of glyphosate as one of the tools in the IPM toolbox is hugely important, it does not fundamentally alter the understanding of invasive weed control in the UK.


Chris Oliver