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Pulsed Water Mists for Suppression of Strawberry Powdery Mildew
Belachew Asalf1, Rodrigo B Onofre2, David M Gadoury3
1Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research (NIBIO), 1431 Ås, Norway.
Abstract:
Powdery mildew (Podosphaera aphanis) is a destructive and widespread disease of strawberry (Fragaria × ananassa), especially when susceptible cultivars are grown in high plastic tunnels or glasshouses. Many powdery mildews thrive in humid environments but free water films on plant surfaces can inhibit conidial germination of some species. We hypothesized that P. aphanis might be directly suppressed by rain through the action of water films and meteoric water. In repeated experiments, the hydrophobic conidia of P. aphanis collected on the surface of water droplets, resulting in their removal when the droplets rolled over the leaf surfaces and fell to the ground. Meteoric water and water films also damaged conidiophores. Brief midday water mists applied in pulses lasting 1 min each four times per day were as effective as multiple fungicide treatments in suppressing powdery mildew. Rapid drying of the pulsed mists resulted in effective suppression of powdery mildew without consequent increases of fungal pathogens that might benefit from water films. The timing and duration of water sprinkling has been refined to the point where it can provide a commercially relevant degree of suppression of powdery mildew on strawberry in a high-tunnel production system.
Insights
Water mists can effectively suppress strawberry powdery mildew (Podosphaera aphanis) by washing away spores and damaging fungal structures. This method offers a fungicide-free alternative for high-tunnel strawberry production.
Area of Science:
- Plant pathology
- Horticultural science
- Agricultural entomology
Background:
- Powdery mildew (Podosphaera aphanis) significantly impacts strawberry (Fragaria × ananassa) yield, particularly in controlled environments like high plastic tunnels.
- While humidity favors many mildews, water films can inhibit spore germination, suggesting a potential role for water in disease suppression.
- The efficacy of water application against P. aphanis, especially in commercial settings, requires further investigation.
Purpose of the Study:
- To investigate the potential of water films and meteoric water in suppressing Podosphaera aphanis on strawberries.
- To evaluate the effectiveness of pulsed water misting as a disease management strategy.
Main Methods:
- Experiments were conducted to observe the interaction of P. aphanis conidia and conidiophores with water droplets and films.
- Pulsed midday water misting (1-minute intervals, four times daily) was applied to strawberry plants in a high-tunnel system.
- Disease suppression was compared between water misting treatments and conventional fungicide applications.
Main Results:
- Hydrophobic P. aphanis conidia were removed from leaf surfaces by rolling water droplets, and water films damaged conidiophores.
- Pulsed water misting demonstrated efficacy comparable to multiple fungicide treatments in suppressing powdery mildew.
- Rapid drying following misting prevented increased incidence of other pathogens that thrive in persistent wetness.
Conclusions:
- Water films and pulsed misting can physically dislodge and damage P. aphanis spores and structures, respectively.
- Optimized water sprinkling provides a commercially viable, non-fungicidal method for managing strawberry powdery mildew in high tunnels.
- This approach offers a sustainable alternative to chemical fungicides, reducing reliance on pesticides in strawberry cultivation.
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