Rovensa Next and Evonik Share Insights Into New Formulations (Part 2)
18 June 2025 AgriBusiness Global continues the conversation with Sara Monteiro, Head of Global R&D Biocontrol and Adjuvants for Rovensa Next, and Lesley A. Schmid, Global Account Manager, Agro for Evonik, with questions from the webinar’s audience. Read more in Part 1 here.
ABG: How much influence does particle size have on spreadability or penetration especially for biologicals?
Lesley Schmid
Lesley Schmid (LS): There is an impact. Larger particle size decreases the homogenous distribution in the spread water film. From our studies with chemical active ingredients, we know if penetration is needed, particle size is optimum between 2-4 micron. Special additives that increase swelling of cuticle and lower the surface tension of water are necessary.
Sara Monteiro (SM): Particle size plays a critical role in the spreadability, penetration, and overall efficacy of biological formulations, especially for microbial products to be used as biopesticides.
For spreadability, smaller particles (typically <10 µm) tend to spread more uniformly on plant surfaces due to better suspension stability and lower sedimentation rates. Surface tension and viscosity of the formulation also interact with particle size to affect how well the product spreads. For penetration and uptake, smaller particles can penetrate stomata or adhere better to leaf surfaces, especially under high humidity. However, too small (<1 µm) may lead to drift and loss during spraying. In soil applications, particle size affects mobility in soil pores. Smaller particles can move more freely but may also leach away. Larger particles may stay localized, which is beneficial for root colonization but limits broader distribution.
One important aspect is microbial viability, mechanical stress during milling or homogenization to reduce particle size can damage microbial cells or spores. It is important to note that particle size also affects shelf life, suspension stability, and compatibility with other tank-mix partners.
ABG: Are you expecting a United Nations Food and Agriculture Organization (FAO) specifications for biological formulations?
LS: In our experience the registration of both chemical and biological formulations is regulated at a country level.
Sara Monteiro
SM: Yes, the FAO, in collaboration with the World Health Organization (WHO), is actively working on specifications for biological formulations, including microbial pesticides. FAO/WHO has published manuals and templates specifically for microbial formulations to guide manufacturers in preparing data submissions
These include guidance on viability and identity of microbial strains, contaminant limits, formulation stability, and efficacy and safety data.
While the most recent detailed specifications are still largely focused on chemical actives, the infrastructure and procedural framework for biologicals is in place and evolving. The FAO is expected to expand and formalize specifications for biologicals as their use becomes more widespread and as regulatory demand increases.
ABG: Are we close to any harmonization (in terms of registration) within EU?
LS: We do not have full insight, but we don’t expect to see harmonization in the short term.
SM: The European Union is making progress toward harmonizing the registration of biological products, particularly microbial plant protection products, but full harmonization is still evolving.
In recent developments (2025), the EU Pesticide Renewal Monitor add updates to the EU Pesticides Database reflect ongoing efforts to streamline data sharing and transparency.
The remaining challenges are mainly linked with Divergent National Interpretations: Despite the zonal system, Member States often interpret data requirements differently, leading to delays. The current framework for the data requirements for microbials is still largely modeled on chemical pesticides, which can be inappropriate or overly burdensome for biologicals.
Finally, while some guidance documents exist there is still a need for clear, harmonized protocols tailored to microbial and natural-origin products.
ABG: Could you speak to trends and challenges for formulations of RNA products?
LS: We are still learning a lot about RNA formulations, please reach out if you’d like to have a further discussion.
SM: Formulating RNA-based products for agricultural applications is a rapidly advancing field, driven by the promise of highly specific, environmentally friendly pest and disease control. However, it comes with a unique set of technical, regulatory, and economic challenges.
RNA is highly susceptible to UV light, RNases, and environmental degradation. Technologies like encapsulation or stabilizers to maintain efficacy in field conditions are very important. The use of lipid nanoparticles, clay nanosheets, or polymeric carriers to protect RNA from degradation is key for stability.
Efficient delivery systems are also a challenge since the RNA products must penetrate cuticles or cell walls without harming the plant.
RNA synthesis is still more expensive than traditional pesticides, scaling up production while maintaining purity and functionality is a major hurdle.
Finally, the regulatory frameworks are not yet fully harmonized, especially in the EU. Questions remain about environmental fate, off-target effects, and resistance management.
ABG: Most / all microplastics seem to be polyurethanes, which have very low biodegradation, what about polyesters?
LS: The ability to pass biodegradability testing will be dependent on the specific polyester molecule. We typically test biodegradability using OECD 301 F.
ABG: What are the performance requirements for the ideal built-in adjuvant?
LS: The ideal built-in adjuvant must exhibit a homogenous distribution in the formulation and be well dispersed in the final tank mix blend. Evonik offers adjuvants with a range of physical properties and performance attributes to fit your specific needs.
ABG: How do you increase the efficacy of an active ingredient such as Beauveria bassiana in the formulations?
SM: To increase the efficacy of an active ingredient like Beauveria bassiana in agricultural formulations, several formulation and delivery strategies can be employed. These aim to enhance spore viability, persistence, infectivity, and target interaction.
Below are some examples:
- For microencapsulation, you can encapsulate spores in biodegradable polymers (e.g., alginate, chitosan) to protect from UV radiation and desiccation, enable controlled release, and improve shelf life and field persistence.
- For oil-based formulations, oil dispersions or emulsifiable concentrates can enhance adhesion to insect cuticles, improve spore survival under dry conditions, and reduce evaporation and wash-off.
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