The Importance of Environmental Monitoring in Botrytis Reduction

Introduction about Botrytis reduction

Botrytis cinerea, commonly known as gray mold, is a common fungal pathogen that causes significant economic damage in horticulture and floriculture due to reduced flower quality and post-harvest longevity (Williamson et al., 2007). Effective environmental monitoring is a crucial component of integrated pest management (IPM) strategies to prevent Botrytis outbreaks. By maintaining optimal growing conditions, cultivators can suppress fungal developement while minimizing chemical interventions (Elad et al., 2016).

This report shows how precise environmental monitoring: focusing on humidity, temperature, air circulation, and leaf wetness, can significantly reduce Botrytis infestation in floriculture.

Botrytis cinerea: Environmental Favorability and Disease Cycle

Botrytis is adapted to cool (15–25°C), humid (>85% RH) environments, with spores germinating rapidly under prolonged leaf wetness (Jarvis, 1977). The fungus spreads via airborne conidia, that infect flowers, stems, and foliage, especially in dense canopies with poor ventilation (Dean et al., 2012). Key environmental factors include:

- High Relative Humidity (RH): Sustained humidity above 85% supports spore germination (Holz et al., 2007).

- Condensation and Leaf Wetness: Free moisture for 6–12 hours allows infection (Dik & Wubben, 2004).

- Airflow: Unventilated air (Stagnant air) increases spore retention and disease spread (Nicot et al., 2016).

- Temperature Fluctuations: Cool nights followed by warm days promote condensation (Fernández & Tello, 2011).

Key Environmental Monitoring Strategies for Botrytis Reduction

1. Humidity Control

- RH Monitoring: Automated sensors can keep the Relative Humidity below 80% which can significantly reduce Botrytis risk (Pineda et al., 2020).

- Vapor Pressure Deficit (VPD): Keeping VPD between 0.8–1.2 kPa reduces leaf wetness duration (Reichardt et al., 2019).

2. Temperature Control

- Avoid Optimal Botrytis Temperatures: Heating greenhouses at night (1–2°C above outdoor temperatures) avoids dew formation (Elad et al., 2011).

3. Airflow and Ventilation Optimization

- Horizontal Airflow Fans (HAF): Improve air circulation, breaking up spore settlement (Nicot et al., 2016).

- Automated Ventilation: Reduces humidity spikes by exchanging humid air (Fernández & Tello, 2011).

4. Leaf Wetness Monitoring

- Electronic Leaf Wetness Sensors: Help adjust irrigation timing to minimize infection windows (Dik & Wubben, 2004).

- Sub-Irrigation Systems: Reduce leaf wetness compared to overhead watering (Pineda et al., 2020).

5. Data Integration and Predictive Modeling

- IoT-Based Climate Control: Automated adjustments reduce Botrytis risk (Reichardt et al., 2019).

- Botrytis Risk Index (BRI): Predicts outbreaks using environmental data (Holz et al., 2007).

Case Study: Environmental Controls in Rose Production

A study in Dutch rose greenhouses showed that automated humidity control reduced Botrytis incidence by 30% (Pineda et al., 2020), and another trial demonstrated a 20% decrease in fungicide use with optimized airflow (Nicot et al., 2016).

The Role of VPD (Vapor Pressure Deficit)

What it is VPD? VPD is the difference between the amount of moisture in the air and the amount of moisture the air can hold when it’s saturated. It is a more important measure to relative humidity (RH) for plant health as it also accounts for temperature.

Low VPD (< 0.5 kPa): Air is near saturation (high RH). Water evaporation from leaf surfaces is limited. This creates a film of free water, which is the primary condition for botrytis spores to germinate and infect.
Optimal VPD (0.8 – 1.2 kPa for many crops): There is an optimal value for the plant to transpire effectively. This movement of water through the plant helps transport nutrients and cools it. Therefore, the leaf surface remains dry, preventing Botrytis spore germination.
High VPD (> 1.5 kPa): Air is very dry. The plant will close its stomata to prevent excessive water loss, effectively decreasing photosynthesis and leading to stress.

How VPD directly reduces Botrytis:

Physical Barrier: Maintaining an adequate VPD ensures the leaf surface is dry, creating a physical barrier that prevents botrytis spores from germinating. A spore can land on a leaf, but without liquid water, it remains dormant.
Reduces Free Water: It prevents condensation on plant tissues (leaves, flowers, stems) and on the inside of the greenhouse structure, eliminating the primary infection sites.

Conclusion

Environmental monitoring is essential for sustainable Botrytis reduction in floriculture. By integrating climate data, cultivaters can suppress fungal outbreaks while reducing chemical dependency.

Recommendations for Floriculturists:

1. Implement environmental sensors (Reichardt et al., 2019).

1. Optimize ventilation and heating (Elad et al., 2011).

1. Drip irrigation to minimize leaf wetness (Dik & Wubben, 2004).

1. Implememt predictive modeling for early intervention (Holz et al., 2007).

References

- Dean, R., et al. (2012). “The Top 10 fungal pathogens in molecular plant pathology.” Molecular Plant Pathology, 13(4), 414-430. DOI: 10.1111/j.1364-3703.2011.00783.x

- Dik, A. J., & Wubben, J. P. (2004). “Epidemiology of Botrytis cinerea in greenhouses.” In Botrytis: Biology, Pathology and Control (pp. 319-333). Springer. DOI: 10.1007/978-1-4020-2626-3_18

- Elad, Y., et al. (2011). “Climate change impacts on plant pathogens and plant diseases.” Journal of Crop Improvement, 25(1), 1-29. doi.org/10.3389/fpls.2022.1032820

- Fernández, J. A., & Tello, J. C. (2011). “Environmental control of Botrytis in greenhouse crops.” Acta Horticulturae, 893, 87-94. DOI: 10.17660/ActaHortic.2011.893.6

- Holz, G., et al. (2007). “Development of a weather-based predictive model for Botrytis cinerea infection.” Plant Disease, 91(5), 504-512. DOI: 10.1094/PDIS-91-5-0504

- Nicot, P. C., et al. (2016). “Management of Botrytis in greenhouse vegetables.” Agronomy for Sustainable Development, 36(1), 1-20. DOI: 10.1007/s13593-015-0341-y

- Pineda, A., et al. (2020). “Smart greenhouse climate control reduces Botrytis in roses.” Biosystems Engineering, 193, 1-10. DOI: 10.1016/j.biosystemseng.2020.01.016

- Reichardt, M., et al. (2019). “IoT-based climate control for disease prevention in floriculture.” Computers and Electronics in Agriculture, 162, 882-891. DOI: 10.1016/j.compag.2019.05.034

- Williamson, B., et al. (2007). “Botrytis cinerea: the cause of grey mould disease.” Molecular Plant Pathology, 8(5), 561-580. DOI: 10.1111/j.1364-3703.2007.00417.x