How to Use Borax to Kill Powdery Mildew

Use borax to kill powdery mildew, resulting in healthy plants.

Powdery mildew is a type of fungal growth on plants that starts as small white spots and gradually becomes a dusty white to gray coating. The mildew can be seen on plant leaves and other plant surfaces. The fungus may affect plant growth and stunt or distort leaves, buds, growing tips and fruit. Fungicides containing borax, or sodium tetraborate decahydrate, can be used to treat the disease. Powdery mildew often grows in humid areas, and borax is effectively mobile in wood with high moisture levels, so it can work effectively on humid plants. Borax also has lower toxicity levels than other fungicide ingredients, such as sodium fluoride.

Things You'll Need

• Borax fungicide
• Gardening gloves
• Garbage bag
• Water
• Baking soda
• Dish liquid
• Spray bottle

Instructions

1. Put on gardening gloves. Gather up all fallen leaves from the affected plant and dispose of them in a garbage bag. Close it tightly.

2. Mix 1 qt. of water with 1 tsp. baking soda and a few drops of dish liquid. Spray the affected plants. This will help the fungicide kill the mildew by causing the surface pH of the plant to become incompatible with powdery mildew spores.

3. Spray the plant with a borax fungicide. Thoroughly cover all plant parts.

4. Follow the fungicide's instructions carefully. Spray the plant in timely intervals, as instructed, until the powdery mildew is gone.

5. Spray surrounding plants with the fungicide to prevent the development of powdery mildew. Do this as often as the instructions direct.

6. Check the plants regularly for signs of powdery mildew, such as white patches with small black dots, distorted plant parts or yellowing leaves.

Tips & Warnings

• Water your plants in the morning, giving them ample time to dry during the day. This will prevent humidity around the plants. Avoid overcrowding the plants. When they are bunched close together, it may encourage mildew growth. Plant in full sun or use shade-tolerant plants that are resistant to mildew.

• Do not spray fungicide on a windy day. Avoid contact with skin. If contact occurs, wash with soap and water.

References

• Osmose Utilities Services, Inc: Technical Bulletin
• United States Forest Service: Borax
• Cornell University: Powdery Mildew
• Lawn Care: Powdery Mildew Treatment and Prevention -- Keeping Lawns Healthy
• Ohio State University: Greenhouse Tomatoes