Clarity Comes to Biostimulants

Product updates

Source adapted from: Daniel Lightfoot, Syngenta Ornamentals United Kingdom (2021).

What do biostimulants contain and what do biostimulants do?

I don’t think it’s too far-fetched to suggest that by the end of the decade we’ll be applying biostimulants to our crops as routinely as we now use fertilisers, fungicides and biocontrol agents.

The last 20 years or so have seen an exponential leap in the amount of research published on biostimulant materials and their effects on crops, which is being reflected in a whole new generation of scientifically supported, specifically targeted products coming onto the market. HICURE, our new amino-acid based biostimulant designed to improve plant tolerance to stresses such as drought and high temperatures, is a good example.

Biostimulants are about to come under a new regulatory regime that for the first time will, among other things, require manufacturers to support any label claims with trials data, as already happens with crop protection products. 

We’re also seeing more agreement on how to define a biostimulant, and how to describe the different kinds of biostimulant product according to their ingredients and their effects on crops. That means you’re likely to be seeing certain terms and phrases more often in product literature and on labels.

What is a biostimulant?

The new regulations define biostimulants as products containing substances and/or microorganisms which, when applied to plants or to the root zone, stimulate natural processes to benefit uptake or more effective use of nutrients, increase stress tolerance or enhance crop quality, independently of their nutrient content.

The European Biostimulants Industry Council, of which Syngenta is a member, classifies plant biostimulants based on their effects when used as recommended, together with their ingredients and relative concentration, dosage, timing, application method and target crops.

The Council says the reason products are best classified according to what they do, rather than by what they contain, is because we’re talking about a wide range of substances, some of which have different effects depending on how they are used and whether they are applied on their own or in a mixture.

The types of ingredient

We can recognise three main types of substance used in biostimulants:

Organic acids

These include amino acids (such as in HICURE) and humic substances derived from composted plant or animal material which aid root growth and nutrient uptake.


Includes seaweed extracts; chitin, or its derivative chitosan (a polysaccharide derived from crustacean shells which stimulates plant pest defense mechanisms); phenolic compounds and a range of other biological or botanical extracts.


These can be beneficial fungi such as soil-dwelling Trichoderma species, or the mycorrhizae that form relationships with plant roots and aid nutrient uptake and stress tolerance; beneficial bacteria such as certain species of Bacillus, Pseudomonas and nitrogen-fixing Rhizobium species; or compounds derived from microbial activity, such as fluvic acids.

Other types of substance include beneficial elements such as silicon, which has no direct nutritional effect but does have a role in stress tolerance; proteins and other nitrogen compounds; inorganic acids and phosphates; and anti-transpirants including waxes.

Any individual product could contain ingredients from more than one of these groups.

Some chemical elements and nitrogen compounds found in biostimulants are also commonly used as fertilisers; while some beneficial organisms, Trichoderma for example, are the active substances of biopesticide products governed by crop protection product regulations when their target is a pest or disease.

Even if some of their ingredients appear to be the same, the amounts present and their effects when the product is used as intended, is what distinguishes a biostimulant from a biopesticide. A biological product that works only by affecting some aspect of the crop’s metabolism – rather than having a direct impact on a pest or pathogen or offering direct protection from them – is a biostimulant; one that has a direct effect on the behaviour or survival of pests or pathogens is a biopesticide (so has to be an authorised crop protection product) or a biological control agent.


The types of action

There are four biostimulant functions;

Nutrient use efficiency

This includes products such as those based on mycorrhizae, designed to help crops take up and use nutrients more efficiently.

Availability of nutrients in soil or rhizosphere

For example, biological nitrogen fixation or improving the solubility of an element such as phosphorus.

Crop quality effects

Biostimulants designed to improve attributes such as flower size or crop shelf-life.

Tolerance to abiotic stress

Products that improve the plant’s ability to withstand conditions such as drought, heat, or high salt levels.

As with the classification of ingredients, the definitions are not mutually exclusive and many products are likely to fulfill more than one function. HICURE, for example, aids a crop’s tolerance to stress and also extends shelf-life.

Choosing and using biostimulants is going to get easier. Make sure the manufacturer is giving you the evidence to support the claims being made for a product and look for named ingredients and microbial species on labels and in literature.

For our part, we’re committed to developing biostimulants and other biological tools to use as part of your integrated pest and disease management programs, and to make what we tell you about them clear and science-based.