What Is Powdery Mildew?
Powdery mildew is a common fungal disease that appears as white or gray powdery spots on leaves. It thrives in moderate temperatures (60-80°F) with high humidity and poor air circulation. Unlike many fungi, it does not need wet leaves.
Which Plants Are Affected?
Most common on cucurbits (cucumbers, squash, zucchini), tomatoes, peppers, and peas. Different species affect different plants, so mildew on cucumbers will not spread to roses.
Prevention Through Spacing
Proper spacing is your first defense. Crowded plants create humid pockets where mildew thrives. Follow spacing recommendations for good air circulation.
Watering Practices
Water at the base, not overhead. Wet foliage promotes mildew. Use drip irrigation. If overhead watering is necessary, do it in the morning so leaves dry quickly.
Resistant Varieties
Look for PM-resistant varieties. Cucumbers like Diva and Sugar Crunch have good resistance. Butternut squash is more resistant than other winter types.
Natural Treatments
If mildew appears, treat immediately: baking soda spray (1 tbsp baking soda + 1/2 tsp soap + 1 gallon water), neem oil, or milk spray (1 part milk to 9 parts water). Remove severely infected leaves.
Long-Term Prevention
Rotate crops, clean up debris, choose resistant varieties, and maintain healthy soil. Stressed plants are more susceptible. These strategies greatly reduce powdery mildew impact.
