Have you ever noticed a white dusting on the leaves of your plants? It might not be what you think. When white or gray powdery spots appear, sometimes covering an entire leaf, it could be a sign of powdery mildew. Here’s what you need to know:
What to Look for
Other symptoms of powdery mildew include yellowing or browning foliage that eventually causes the plant to prematurely defoliate. For flowers and trees, this fungus can cause early bud drop and decrease flower quality. Fortunately, powdery mildew is rarely fatal to a plant.
Powdery Mildew Prevention
Powdery mildew thrives in conditions including dry foliage, humid, low light, and moderate temperatures. You can minimize the risk of this disease by:
- Planting disease-resistant plant varieties.
- Maintaining air flow between plants by not overcrowding them.
- Placing plants in an area where they will receive sufficient light for at least six hours per day.
- Regularly trimming back trees and shrubs that block light.
- Using a slow-release fertilizer, as over fertilization can make your plants more susceptible to disease.
Powdery Mildew Treatment
Set aside a regular time to monitor your garden for disease. Early detection is your best chance at eliminating the problem. If you find an affected plant, here are your best treatment options:
- Use a fungicide with the active ingredient “chlorothalonil.” This is proven effective, but leaves the plant surface with a while milky film.
- Combine baking soda with horticultural grade or dormant oil and liquid soap, applying in the early stages of the mildew outbreak. Continue to spray this solution on plants every one to two weeks.
- For an organic solution, use Safer® Brand’s sulfur-based fungicide. Potassium bicarbonate, another solution approved for use in organic growing, kills mildew spores right away.
- The acetic properties of apple cider vinegar can help control this disease. Mix two to three tablespoons with a gallon of water. Be careful when mixing, as too much vinegar can burn your plants.