Are there any natural enemies of cereal diseases, such as ergot?

There is a need to drive down ergot levels in UK grain and all management options are on the table. Ellie Dearlove examines whether natural enemies can really make a difference to disease control in cereal crops.

We have received a few questions in the AHDB letterbox asking if natural enemies contribute to crop disease control, especially for ergot.

Well, for ergot, the short answer is that there is no hard evidence of natural enemies directly reducing ergot infection. However, some do reduce the survival and spread of other crop pathogens. There is also some evidence of biopesticide efficacy against ergot – so nature-inspired approaches could be part of the solution.

Natural enemies come in many shapes and sizes. Here are some ways they can reduce pathogens. 

• Soil microbes: some fungi and bacteria stop pathogens germinating by destroying their resting structures. For example, certain soil microbes (e.g. some Trichoderma and bacterial species) break down Sclerotinia sclerotiorum’s resting bodies (sclerotia)

• Soil invertebrates: nematodes, mites, springtails and earthworms can graze on fungal structures (spores or hyphae) on or in the soil. Some insects even nibble away at fungal fruiting bodies 

• Vector predators: some insects spread disease (e.g. aphids or thrips). When beneficial invertebrates, including ladybirds, hoverflies and parasitoid wasps, reduce disease vectors, they contribute indirectly to disease control

• Microbial competition: some microbes compete with pathogens for nutrients or space; others secrete natural antibiotics. Examples include Bacillus subtilis, Pseudomonas fluorescens and some fungal species, including Trichoderma species
• Soil engineers: numerous organisms alter soil conditions, which may help reduce soilborne disease pressures

• Endophytes: some microbes live inside plant tissues and may contribute to crop pathogen defences

Despite the lack of evidence of a direct impact of natural enemies on ergot, we know that:

• Some biopesticides may potentially reduce or delay the germination of ergot sclerotia or control infection in cereal ears
• Various natural enemies (e.g. carabid beetle species, such as ground beetles) feed on the seed of grass species. As many grass species (including black-grass) also host ergot, they can contribute to disease spread. Therefore, seed feeding may control disease indirectly
• Many insects are attracted to spore-containing honeydew produced by ergot-infected ears. We know that moths, flies, leafhoppers and thrips can spread secondary ergot spores (conidia) in this way

There is uncertainty about the specifics, but encouraging biodiversity and beneficial organisms can contribute to overall disease control.

To provide a natural boost:

• Improve soil health: use organic amendments to modify soil microbiota and suppress soilborne pathogens. This may either be a general effect (from overall microbial diversity) or a specific effect (from key species)

• Control weeds: manage grass weeds to reduce ergot risk directly. Also support carabid beetles to add an extra weed-seed-predation layer
• Manage habitat: embrace flower strips and beetle banks to support predator and decomposer populations

Be aware that recent incentives that promote the use of flower-rich grass margins, grass buffer strips and grassy field corners may have contributed to a rise in ergot prevalence (alongside herbicide-resistant grass weeds, shorter rotations and reduced tillage). It is important to manage seed mixes and margins carefully to avoid susceptible grass species spreading ergot.

Our recent review of ergot management considered biological control options (see page 35 of Research Review 102).

Some biopesticides are already used to control plant diseases in other countries and cropping situations. For example, some seed coating or soil inoculant products based on endophytic (e.g. Trichoderma), mycoparasitic fungi and bacteria are used to manage root diseases, such as those caused some by Pythium and Fusarium species. Some of these products have demonstrated potential to reduce or delay the germination of ergot sclerotia.

Check out the practical ergot management tips based on our research review findings.

This autumn, new AHDB-funded pilot trials will get underway to test biofungicide efficacy in wheat. Although the pilot will focus on septoria tritici, it will help underpin the wider adoption of biopesticides in cereals and oilseeds.

The AHDB Agronomy Conference on 9 December 2025 (in Solihull) will include the latest thinking on ergot management. Keep an eye on our agronomy event page for details.

Use the AHDB soil health scorecard to monitor and manage soil health on a rotational basis.