Baking soda can be a helpful tool in Plumeria care, primarily for its fungicidal properties and as a mild natural pesticide. Here’s how you can use baking soda to benefit your Plumeria plants:

1. Fungal Disease Prevention and Treatment:
   • Mildew and Fungus Control: Baking soda can help prevent and treat mild fungal diseases such as powdery mildew, a common issue in plants, including Plumeria.
   • How to Use: Mix 1 tablespoon of baking soda with 1 gallon of water. You can also add a small amount of liquid soap to help the mixture adhere to the leaves. Spray this solution on the Plumeria’s leaves, covering both the top and bottom surfaces.
2. Pest Deterrent:
   • Natural Pesticide: While not a strong pesticide, baking soda can deter some pests when used as a foliar spray.
   • Application: The same mixture used for fungal prevention can be applied to deter pests. However, its effectiveness on pests is limited and should not be relied upon as the sole pest control method.
3. Soil pH Adjustment:
   • Altering pH: Baking soda is alkaline and can be used to make soil more alkaline if needed. However, this should be done cautiously, as Plumeria generally prefer slightly acidic to neutral soil.
   • How to Apply: Only use baking soda to adjust soil pH after testing the soil. It’s more commonly used to raise the pH of overly acidic soil.
4. Leaf Shine:
   • Cleaning Leaves: A mild solution of baking soda and water can be used to wipe down leaves, removing dust and grime. This can improve photosynthesis and overall plant health.

Caution in Using Baking Soda:

• Risk of Overuse: Overusing baking soda, especially in high concentrations, can damage Plumeria plants. It can lead to leaf burn and can upset the natural pH balance of the soil.
• Test First: Before applying broadly, test the baking soda solution on a small area of the plant to ensure it doesn’t cause damage.
• Avoid Strong Sunlight: Do not spray baking soda solutions on plants during strong sunlight, as this can increase the risk of leaf burn.
• Not a Replacement for Fungicides: For severe fungal infections, commercial fungicides or other proven treatments should be used.

In summary, while baking soda can be a useful addition to your Plumeria care routine, particularly for mild fungal issues and as a gentle leaf cleaner, it should be used judiciously and with care to avoid potential plant damage.