Soil fungus could replace chemical sprays in fight against crop diseases

A common soil fungus known to boost plant health could help farmers reduce their use of synthetic sprays to manage crop diseases.

Scientists at Rothamsted Research, working with teams from the Universities of Exeter and Warwick, have found that Trichoderma hamatum – a fungus already known to protect plants – releases natural airborne vapours that stop harmful pathogens from growing.

In tests, these vapours, known as volatile organic compounds (VOCs), were shown to hold back the advance of Sclerotinia sclerotiorum, a pathogen that attacks over 800 plant species worldwide, including lettuce, beans, carrots, oilseed rape and potatoes.

The fungus forms long-lived resting structures called sclerotia that survive in soil for up to eight years, making crop rotation and tillage largely ineffective. Farmers have long relied on chemical fungicides to protect crops, but resistance is on the rise and regulations are tightening in both the UK and EU, prompting the need for alternative measures to be found.

Natural protection from the soil

In work published in Environmental Microbiology Reports, researchers grew Trichoderma side by side with Sclerotinia in the lab. When the two fungi “met,” Trichoderma began to pump out a stronger mix of natural chemicals into the surrounding air. After seven days these invisible vapours slowed down and in some cases completely stopped the disease fungus.

One compound in particular, called 1-octen-3-one, proved especially powerful. At very small doses, it not only halted Sclerotinia but also blocked the growth of other serious crop diseases including grey mould (Botrytis cinerea), light leaf spot in oilseed rape (Pyrenopeziza brassicae), and take-all in wheat (Gaeumannomyces tritici).

Trichoderma is already used in some biocontrol products, such as seed coatings or soil amendments, because it competes with harmful fungi and helps plants strengthen their defences. This latest research suggests that its airborne signals may be just as important as its direct interactions in the soil.

Promise and caution for field use

While results in the laboratory have been positive, the researchers say the next step is to test these natural chemicals in glasshouses and field plots.

Getting the right doses is also important — while low levels of 1-octen-3-one killed fungi, higher levels can sometimes stunt plant growth.

The researchers say that refining the right mix and concentration will be vital before any commercial product reaches the market. If these natural compounds can be stabilised, concentrated, or encouraged in soils, they could form the basis of a new generation of sustainable fungicides.

“Further work is needed to understand how these fungal VOCs operate in real-world farming conditions, and whether they can be harnessed effectively at scale,” said Dr Jozsef Vuts, chemical ecologist at Rothamsted and a co-author of the study. “But the discovery offers fresh hope for greener crop protection at a time when agriculture is under pressure to cut chemical inputs.”