Wood-based biochar could make beneficial fungal biopesticides easier to apply and store
Researchers identify which biochars work best as solid carriers for Trichoderma-based biopesticides
image: Wood-based biochars produced at low pyrolysis temperatures are good carriers for a Trichoderma-based biopesticide
Credit: Jane Debode, Jarinda Viaene, Kristof Maenhout, Lisa Joos, Soraya C. França, Ann Cuypers & Bart Vandecasteele
Applying beneficial microbes to soil sounds simple, but in practice it can be difficult to distribute small amounts of microbial products evenly through growing media or field soils. A study published in Biochar suggests that carefully selected biochar could help solve this problem.
Researchers tested whether biochar, a carbon-rich material made by heating biomass in limited oxygen, can serve as a solid carrier for a commercial Trichoderma-based biopesticide. Trichoderma fungi are widely used in agriculture because they can help suppress plant pathogens, compete with harmful microbes, and support healthier plant growth. However, keeping these living organisms viable and easy to apply remains a key challenge for biocontrol products.
In the study, the team evaluated 35 different biochars made from wood, manure, and other biomass sources, including coffee grounds, spent growing media, flax shives, and greenhouse waste. The biochars were produced at different pyrolysis temperatures, ranging from 300 to 750 °C. Each biochar was inoculated with ASPERELLO® T34 Biocontrol, a commercial formulation containing Trichoderma asperellum T34, and then incubated for eight weeks at 15 °C.
The results showed that not all biochars are equally suitable for carrying beneficial fungi. Biochars made from wood-based feedstocks and produced at lower pyrolysis temperatures, especially 300 to 450 °C, performed best. These materials were more likely to maintain or support the survival of Trichoderma during incubation. In contrast, manure-based biochars and biochars produced at higher temperatures were generally less effective carriers.
“Our results show that biochar is not a one-size-fits-all carrier,” said corresponding author Dr. Jane Debode of the Flanders Research Institute for Agriculture, Fisheries and Food. “The feedstock and production temperature strongly influence whether a biochar can support a living biocontrol fungus. Selecting the right biochar could make microbial biopesticides easier to use in soil and growing media.”
The team also identified chemical traits linked to better Trichoderma carrier capacity. Good carrier biochars tended to have higher water-soluble carbon, lower pH, lower inorganic carbon, and lower total phosphorus content. These properties may create a more favorable environment for fungal survival. Higher pyrolysis temperatures often produce more recalcitrant biochars with fewer easily available carbon sources, which may make them less useful for supporting microbial growth.
Among the 35 tested biochars, ten were considered good carriers because they maintained or increased the initial Trichoderma population after incubation. To test whether the best candidates could also support longer-term storage, the researchers selected four inoculated biochars for an additional cold-storage experiment. After 26 weeks at 4 °C, the selected biochars maintained similar levels of Trichoderma, suggesting that well-chosen biochar may also help preserve shelf life.
“This is an important first step toward more practical biochar-based biocontrol formulations,” said Debode. “A solid premix of biochar and Trichoderma could help growers apply very small doses more evenly before planting.”
The authors note that further research is needed to test whether these findings apply to other Trichoderma strains and formulations, and to evaluate disease-control performance in greenhouse and field trials. Still, the study provides a practical screening framework for selecting biochars that can help carry beneficial microbes into agricultural systems.
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Journal Reference: Debode, J., Viaene, J., Maenhout, K. et al. Wood-based biochars produced at low pyrolysis temperatures are good carriers for a Trichoderma-based biopesticide. Biochar 6, 91 (2024).
https://doi.org/10.1007/s42773-024-00368-5
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.