Powdery mildew, often called “PM”, is a common fungal disease that shows up on many edible plants, especially in warm weather. You'll see it most on squash, zucchini, pumpkins, cucumbers, melons, peas, beans, and brassicas like kale and broccoli. The good news? It's usually easy to manage when caught early.
What does it look like?
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White or light gray circular, powdery spots on leaves or stems
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Spots that spread and merge into fuzzy patches
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Yellowing, curling, or distorted leaves as the infection worsens
Is it harmful?
To people and animals: No. Produce with small amounts of powdery mildew is safe to eat after washing. To plants: Yes. Left untreated, it can slow growth, reduce airflow, and affect plant health and flavor.
How to treat PM
1. Prune affected leaves
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Remove the most heavily infected leaves and stems.
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Don't remove more than 1/3 of the plant at a time.
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Sanitize pruners afterward to avoid spreading spores.
2. Apply a fungicide
Treat both affected and nearby healthy plants. Our recommended option is the Arber Organic Bio Fungicide.
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Active infection: Spray 1–2 times per week.
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Prevention: Spray 1–2 times per month during warm weather.
3. Check nearby plants
Powdery mildew spreads through microscopic airborne spores that can travel long distances on the wind, insects and animals — making it one of the most common plant diseases in home gardens. Inspect nearby plants and weeds, and treat or remove any heavily infected growth when possible.
How to help prevent it
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Harvest and prune regularly to improve airflow.
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Remove yellowing leaves.
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Inspect plants weekly during warm weather.