Opinion: Biostimulants held back by inadequate regulation

For UK wheat producers, weather variability has overtaken traditional agronomy challenges as the biggest threat to crop performance, ahead of disease or weed control.

On top of weather challenges, the sector is under financial strain, as demonstrated by Minette Batters’ 2025 Farming Profitability Review.

While the review’s recommendations are broad, a clear theme has emerged: the need for a stronger regulatory environment that encourages innovations with measurable commercial returns.

See also: Agri-tech must earn its place on-farm 

Biostimulants sit at the intersection of these challenges. Applied to crops or soil, they can help plants cope better with stress and make more efficient use of inputs, so lifting profitability.

Despite this, many UK growers remain sceptical.

Most biostimulants in the market are complex biological extracts with limited information on mode of action and weak evidence of reliable performance on farms.

Unlike plant protection products, they face little oversight when it comes to claims about composition, safety or performance.

As a result, farmers are often asked to trust bold marketing claims with limited independent proof.

Innovation 

A recent survey by Grounded Research reflects this, with respondents rating their experience with biostimulants poorly.

However, three-quarters said they would increase biostimulant use if the benefits were clear and credible. The appetite for innovation exists, but trust is lacking.

In some countries, regulators are beginning to address this gap. In 2019, the EU introduced function-based definitions and a structured process for certifying claims.

In the US, more than a dozen states have added biostimulant definitions to fertiliser regulations, with more expected to follow.

But in the UK, progress has been slow. That delay risks creating two problems.

First, farmers may miss out on credible innovations that improve resilience and profitability.

Second, the absence of clear rules leaves space for “science-washing”, where complex language or academic references are used to promote products inadequately.

Strong pipeline 

This is frustrating given that the UK has a strong pipeline of publicly funded science capable of delivering the next generation of biostimulants.

Hard evidence of this is a “chemical caging” technology developed by Rothamsted Research and the University of Oxford on the back of 20 years of science.

The technology enables caged versions of plant metabolites to be delivered inside cells through a simple foliar spray, where they are released in their active form to stimulate specific processes.

The first molecule in the pipeline, patented by SugaROx, is a caged version of trehalose-6-phosphate (T6P), a plant sugar that inhibits a famine-signalling enzyme called SnRK1.

Extensive testing is underway with ADAS and innovative farmers, supported by Innovate UK, to demonstrate performance under a range of farm conditions.

Step change

Historically, many biostimulants with poorly defined modes of action have delivered modest yield improvements.

More precise approaches currently under development will drive a step change in productivity, but only if farmers can distinguish credible science from marketing claims.

International markets are moving toward evidence-based standards, while UK growers still face a marketplace where claims vary widely in quality. Over time, this risks weakening their  competitiveness.

Hence, Defra now faces a clear choice: introduce a certification system to allow farmers to test and adopt new biostimulants with confidence, or allow “science-washing” to undermine trust for good.

New regulation is needed to turn promising science into practical tools for tackling climate change, the biggest agronomic challenge now facing wheat production in the UK.