Molecular Identification and Control of Strawberry Decay Using Thyme-Rosemary Microencapsulated Oils

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Strawberries, loved worldwide for their sweet taste and bright color, face a major problem: they spoil quickly because of fungi. These fungi attack the fruit in fields, during transport, and even after they are bought, leading to waste and economic losses.

A new study from 2025 offers hope by using natural ingredients—thyme and rosemary essential oils—to fight these fungi. The oils are packed into tiny protective capsules made from corn protein, creating a safe and effective way to keep strawberries fresh longer. This article explains how this method works, why it matters, and how it could change the way we protect our food.

Botrytis Deweyae Threatens Global Strawberry Crops

The study began by identifying two harmful fungi causing strawberry decay. The first, Botrytis deweyae, was originally found on daylilies in the UK but has now been detected on strawberries. This fungus belongs to the Botrytis genus, a group known for causing gray mold and other plant diseases.

Botrytis species are challenging to identify because many look similar under a microscope, but genetic testing helps distinguish them.Conidiophores are erect, septate, colorless to pale brown, with botryose or grape cluster-like structures of conidiogenous cells in the terminal part.

Conidiogenous cells are integrated, polyblastic, and terminal on branches. Conidia are solitary, ellipsoid, ovoid, oblong, hyaline, 0–1-septate, apex obtuse, base truncate with small abscission scar, 8–20 (–25) × 4–8 µm.

Aspergillus Pseudotubingensis Identified in Strawberry Rot

The second fungus, Aspergillus pseudotubingensis, is a newly discovered species within the Aspergillus genus, which includes molds that produce harmful toxins. Unlike some Aspergillus species, A. pseudotubingensis lacks sclerotia—hardened survival structures that help fungi endure harsh conditions—but it still thrives on strawberries, causing rot.

Conidiophores are long (commonly 2–3 mm), stipes are smooth, thick-walled, and light brown. Conidial heads are globose, radiate, dark brown, 100–200 µm in diameter. Vesicles are globose to ellipsoid, variable in size, mostly 40–60 µm in diameter.

Metulae almost cover the entire surface of vesicles (15–40 × 3–5 µm). Conidia are globose to subglobose, dark brown with an echinulate surface, and 3–5 µm in diameter.

How Essential Oils Prevent Post-Harvest Strawberry Loss

Researchers confirmed these fungi using advanced genetic tests. For example, they analyzed the ITS-rRNA region, a segment of DNA commonly used to identify fungi because it varies enough between species but remains stable within them.

They also examined the RPB2 gene, which codes for part of the RNA polymerase enzyme involved in fungal growth, and the β-tubulin gene, critical for cell structure.

By comparing these genetic markers to databases, the team confirmed the fungi were B. deweyae and A. pseudotubingensis. These tests are essential because relying solely on physical traits can lead to misidentification, especially in fungi with subtle differences.

Thyme and Rosemary Oils Outperform Chemical Fungicides

Once the harmful fungi attacking strawberries were identified, the research team began exploring alternative solutions to stop their spread. Traditionally, chemical fungicides like Signum (a combination of boscalid and pyraclostrobin) have been used to combat fungal infections in agriculture. These fungicides are effective in killing fungi, but they come with significant drawbacks.

• One of the main concerns with chemical fungicides is the residues they leave on the fruits.
• These residues can be harmful to human health when consumed, as some chemicals may be toxic or cause long-term health effects.

Furthermore, these chemicals can contaminate the environment, including the soil and water, posing a risk to ecosystems and wildlife. This pollution also affects the sustainability of agriculture, as the soil becomes less fertile over time.

Another issue with chemical fungicides is the development of resistance by the fungi. Over time, as fungi are repeatedly exposed to the same chemicals, they adapt and evolve, making the chemicals less effective. This phenomenon leads to the need for higher doses or new chemicals, which can further increase environmental and health risks.

Zein Microcapsules Enhance Strawberry Shelf Life

Essential oils from thyme and rosemary are known for their strong antifungal properties, making them effective in fighting fungi that attack fruits like strawberries.

However, a major challenge with these oils is that they break down quickly when exposed to air or light, losing their effectiveness.

To overcome this problem, the researchers found a solution by encapsulating the oils inside tiny protective capsules. These capsules are made from zein, a protein extracted from corn, which is both natural and safe for use in food preservation.

The encapsulation process, known as electro-spraying, uses high-voltage electricity to create tiny capsules that are measured in nanometers. These ultra-small capsules act as a protective shield, keeping the oils intact and preventing them from breaking down. As a result, the oils are released slowly over time, providing long-lasting protection against fungal growth, without the oils degrading quickly.

Microencapsulation Technology Preserves Fresh Strawberries Longer

The thyme and rosemary oils were analyzed using gas chromatography-mass spectrometry (GC-MS), a technique that separates and identifies chemical compounds. Thyme oil contained high levels of thymol (11.01%), a powerful antifungal compound that disrupts fungal cell membranes, along with p-cymene (8.58%) and γ-terpinene (5.96%), which enhance its antimicrobial effects.

Rosemary oil was rich in α-pinene (8.58%), a compound that inhibits spore germination, 1,8-cineole (13.46%), known for its ability to penetrate fungal cells, and camphor (20.18%), which damages fungal structures.

By combining these oils, the researchers created a potent mixture that targets fungi in multiple ways, such as breaking down their cell walls and stopping spore germination. This multi-target approach reduces the chance of fungi developing resistance, a common issue with single-chemical fungicides.

Eco-Friendly Solutions for Sustainable Strawberry Farming

Next, the team tested how well the encapsulated oils worked compared to chemical fungicides. Strawberries were sprayed with a suspension containing 1×10⁶ spores/mL of B. deweyae and A. pseudotubingensis—a concentration high enough to mimic severe natural infections.

The fruits were then treated with different concentrations of the oil capsules (2.5%, 5%, and 10%) or Signum® (25, 50, and 100 mg/L). Disease severity was scored on a 0–8 scale, where 0 meant no damage and 8 meant over 70% of the fruit surface was rotted.

After 10 days of storage at room temperature (25°C), the results were clear: strawberries treated with the highest concentration of oils (10%) had the least rot.

Reducing Food Waste with Natural Strawberry Preservation

The fruits treated with the oil capsules not only showed protection from fungi but also had other significant benefits. They remained firmer, retained their bright color, and preserved more vitamin C compared to fruits that were untreated or chemically treated. This shows the additional advantages of using the natural oil capsules for food preservation.

The success of these oil capsules can be attributed to their unique design. The zein protein forms a smooth, non-porous shell around the oils, which prevents the oils from evaporating or reacting with air. This protective coating ensures that the oils remain effective for a longer period, offering prolonged protection to the fruit.

Moreover, zein is a biodegradable and edible protein, making it an excellent choice for food applications. It is safe to consume, and importantly, it breaks down naturally in the environment, making it environmentally friendly and sustainable.

Conclusion

In conclusion, this study marks a turning point in food preservation. By harnessing the power of thyme and rosemary oils in innovative capsules, researchers have created a solution that is safer, greener, and more effective than traditional chemicals. For farmers, it offers a way to protect crops without harming the environment or risking chemical resistance.

For consumers, it promises fresher, healthier strawberries free from synthetic residues. And for the planet, it reduces reliance on synthetic chemicals, paving the way for a more sustainable future. As demand for organic food grows—driven by health-conscious shoppers and stricter environmental regulations—such natural innovations will play a crucial role in feeding the world while protecting its resources.