Baking Soda Spray
A simple alkaline spray made from sodium bicarbonate that raises leaf surface pH to create conditions unfavourable for fungal growth.
What it is
Baking soda (sodium bicarbonate) is a common household salt that is inexpensive, readily available, and safe for use around food crops, people, and pets. When combined with a small amount of horticultural or castile soap, it adheres to foliage and creates a preventive fungal barrier. It is approved for organic production when used as described.
What it does
Fungal pathogens typically require a slightly acidic to neutral surface environment to germinate and colonise. Raising the pH of the leaf surface to alkaline conditions (above pH 8) using sodium bicarbonate disrupts spore germination and slows the spread of existing infections. The effect is primarily preventive rather than curative.
When to use
Apply at the very first signs of powdery mildew or leaf spot diseases, or preventively during warm, humid weather when these diseases are most likely. Most effective at halting early-stage disease spread. Spray every 7 days through the risk period and after rain has washed off previous applications.
When not to use
Avoid using on highly salt-sensitive plants or in combination with other foliar sprays that could cause phytotoxicity. Overuse on the same plant can cause sodium accumulation in soil, which inhibits beneficial microbes over time. Do not apply in direct sun or when leaf surfaces are dry and temperatures are high.
How to apply
- 1
Dissolve 1 teaspoon of baking soda in 1 quart of warm water.
- 2
Add 2 - 3 drops of castile soap or horticultural soap to help the spray adhere to leaf surfaces. Stir gently.
- 3
Transfer to a clean spray bottle and use immediately. Do not store mixed solution.
- 4
Spray all affected plant surfaces in the early morning, covering both upper and lower leaf surfaces.
- 5
Repeat every 7 days through active disease pressure, and always reapply after rainfall.
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.