Fungal disease
Squash Powdery Mildew
A very common fungal disease that covers squash leaves in white powder, usually from midsummer.
Symptoms
- White, powdery spots on leaves and stems
- Spots spreading until leaves are coated
- Leaves yellowing, drying and dying early
What causes it
Spores spread on air; warm days, humid nights, crowded plants and dry soil make it worse.
What you can do
- Remove the worst-affected leaves.
- Space plants well for air flow.
- Keep the soil evenly moist, watering at the base.
- Grow resistant varieties; sulphur or potassium bicarbonate sprays can help early on (follow the label).
Not sure it's powdery mildew?
Photograph one affected leaf and Plantulus will suggest the most likely problem, with a confidence score. It's free and needs no sign-up.
Check a leaf photoGeneral guidance only, not a diagnosis. Check product labels and local rules before using any treatment, and ask a horticultural specialist if a valuable plant is struggling. See the disclaimer.