The Invisible Battle: Real Images of Bacillus spp. Biocontrol Against Black Sigatoka
Part 2 – Visual and Comparative Evidence of Biocontrol
Introduction
In the first part of this series, Beyond Fungicides: Biotechnological Strategies for Managing Black Sigatoka, we explored the scientific foundations and integrated strategies to combat this disease that threatens banana and plantain productivity.
In this second installment, we delve into the visual evidence and practical results, showing how Bacillus spp. acts against Pseudocercospora fijiensis, with laboratory tests and field trials that demonstrate its potential as a sustainable alternative to chemical fungicides.
Visual Evidence of Biocontrol
In vitro tests allow us to observe how Bacillus spp. inhibits the growth of Pseudocercospora fijiensis:
– Appearance of inhibition halos around the bacterial colony (Macedo-Raygoza et al., 2019).
– Structural damage to hyphae and conidia upon contact with bacterial metabolites (Cruz-Martín et al., 2020).
Figure 1. Scheme of the confrontation of P. fijiensis against beneficial bacteria
Note: Design obtained from (Molinari & Quintana, 2025)
Figure 2. Proposed mode of action implemented by the microbial biocontrol product based on B. tequilensis EA-CB0015 (WT).
Note: The MBCA product, based on B. tequilensis EA-CB0015 (WT), reduces the severity of Black Sigatoka disease when inoculated on banana and plantain leaves through competition for nutrients and space, and antibiosis. (Cuellar-Gaviria, T. et al., 2021)
Figure 3. Dual antagonism test between Bacillus spp. and Pseudocercospora fijiensis.
Note: Interaction between Black Sigatoka and bacterial strains after 4 days of incubation at 28°C. (Molinari & Quintana, 2025)
Figure 4. Structural damage in fungal hyphae upon contact with metabolites of Bacillus spp.
Note: Effect of the bacterial culture filtrate of Bacillus subtilis strain CCIBP-M27 on conidia and mycelium of Pseudocercospora fijiensis at 48 h of incubation. (Cruz-Martín et al., 2020)
Field and Comparative Results
Trials in Colombia demonstrated that:
– Bacillus subtilis EA-CB0015 reduced the severity of Black Sigatoka by 28.1% with applications every 11 days (Gutiérrez-Monsalve et al., 2015).
– In parallel, the fungicide chlorothalonil reduced the severity by 29.5%, very similar figures.
Furthermore, strains like B. velezensis and B. amyloliquefaciens produce lipopeptidic compounds (surfactin, iturin, fengycin) that alter the fungus’s membrane and stimulate the plant’s natural resistance (García-Giraldo et al., 2022).
Environmental Impact: Bacillus vs. Chemicals
| Aspect | Bacillus spp. (Biofungicide) | Chemical Fungicides |
| Efficacy against P. fijiensis | Moderate reductions (20-30%). Can be integrated with chemicals. | High reductions (>60-80%) but with a risk of resistance. |
| Environmental Persistence | Biodegradable, without toxic residues. | Persistent residues (ETU, metals). |
| Ecological Impact | Minimal, does not affect insects or fauna. | Moderate/High, risk to bees, fish, and amphibians. |
| Resistance | None, multiple mechanisms of action. | High, resistant strains already exist. |
BioNaturaleza: Visible Science at the Service of the Producer
Biocontrol with Bacillus spp. is a proven and sustainable strategy:
– It works in the laboratory and in the field.
– It complements (and in some cases, equals) the effect of chemical fungicides.
– It reduces environmental impact and protects soil health.
If you haven’t yet reviewed the first part of this series, we invite you to read it to understand the context and the integrated strategies that complement these results:
Beyond Fungicides: Biotechnological Strategies for Managing Black Sigatoka
At BioNaturaleza Biotech™, we continue to transform science into visible and reliable tools for the producer.
