Talc-Based Bacillus subtilis Consortium Shows Powerful Eco-Friendly Control of Rice Stem Rot

A new study published in the Journal of Crop Health (2025) demonstrates that a talc-formulated consortium of Bacillus subtilis strains offers a highly effective, environmentally safe strategy to combat rice stem rot caused by Sclerotium oryzae—a major disease impacting rice productivity in Bangladesh.

Rice stem rot is responsible for yield losses of up to 45%, with chemical fungicides historically used as the primary management approach. However, environmental concerns and rising production costs have intensified the search for sustainable alternatives. The newly released research provides strong evidence that biological control agents—particularly B. subtilis—can fill this gap.

Key Findings from the Study

Researchers evaluated 16 isolates of Pseudomonas fluorescens and nine isolates of Bacillus subtilis using in vitro dual culture assays.

The most effective P. fluorescens isolates (Pf-7 and Pf-8) inhibited pathogen growth by 58.06% and 62.02%.
The top-performing B. subtilis isolates (Bs-17 and Bs-41) showed substantially higher suppression, reaching 85.32% and 86.13%.

Following laboratory screening, field trials were conducted using talc-based formulations. The standout treatment—T12, consisting of a 24-hour seedling root dip in a consortium of Bs-17 and Bs-41—achieved disease incidence and severity levels statistically similar to chemical fungicides.

Growth and Yield Improvement

Beyond disease suppression, the T12 treatment significantly improved plant performance:

Plant height: 53.89 cm
Tillers per hill: 25.89
Leaves per hill: 60.44
Grains per panicle: 162.89
Yield: 743.73 g/m² — the highest among all biological treatments

These indicators reveal not only disease control but also enhanced plant vigor and productivity.

Why Talc-Based Formulation Matters

Talc serves as an effective carrier material, protecting microbial cells from desiccation and extending shelf life. In this study, the consortium maintained viable populations for up to four months, making it suitable for field application and potential commercialization.

Implications for Sustainable Rice Farming

While copper oxy-chloride fungicide (T13) still recorded the highest performance, the talc-based B. subtilis consortium offered comparable results without environmental drawbacks. This positions it as a promising alternative for eco-friendly crop protection in rice-based agricultural systems.

Conclusion

The research provides compelling evidence that talc-formulated B. subtilis Bs-17 and Bs-41 applied through 24-hour root dipping can serve as an efficient biological substitute for chemical fungicides against rice stem rot. The authors recommend further multilocation trials to validate the technology for wide-scale adoption.

Reference

Ferdous, Z., Ali, H., Aff, T.A. et al. Eco-Friendly Management of Rice Stem Rot Using Talc-Based Formulations of Bacillus subtilis and Pseudomonas fluorescens. Journal of Crop Health 77, 192 (2025). https://doi.org/10.1007/s10343-025-01252-3