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Powdery Mildew in Spaghetti Squash

verifiedReviewed by the GreenScout Team

Spaghetti squash is a winter squash variety that produces oblong, pale yellow fruits with mild, slightly sweet flesh that separates into thin strands resembling pasta when cooked. A fungal disease that coats leaves, stems, and buds with a white or grey powdery substance. It rarely kills plants but weakens them significantly.

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Spaghetti Squash care requirements

These care conditions are most relevant to powdery mildew in Spaghetti Squash. Check each one as a potential cause.

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Light
Full sun (6–8 hours daily minimum); requires intense light for fruit development and sweetness.
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Water
Water deeply and consistently, providing 1–2 inches per week; reduce watering as fruits mature. Avoid wetting foliage to prevent disease.
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Soil
Well-draining, fertile soil rich in organic matter; pH 6.0–7.5. Amend with compost before planting.
symptoms

Symptoms to look for in Spaghetti Squash

  • fiber_manual_recordWhite or grey powdery coating on leaf surfaces
  • fiber_manual_recordAffected leaves yellowing and curling
  • fiber_manual_recordDistorted or stunted new growth
  • fiber_manual_recordPowdery patches on stems and flower buds
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Common causes in Spaghetti Squash

  • fiber_manual_recordHigh humidity combined with poor air circulation
  • fiber_manual_recordOvercrowded planting conditions
  • fiber_manual_recordWarm days and cool nights
  • fiber_manual_recordExcessive nitrogen fertilisation promoting soft growth
  • fiber_manual_recordWater-stressed plants are more susceptible
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How to diagnose powdery mildew in Spaghetti Squash

The white powdery coating is distinctive — unlike downy mildew, powdery mildew sits on the upper surface of leaves and can be rubbed off with a finger.

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How to treat powdery mildew in Spaghetti Squash

Remove and dispose of affected leaves. Spray with a diluted solution of baking soda (1 tsp per litre of water) or neem oil. Ensure good air circulation around the plant. In severe cases, use a fungicide labelled for powdery mildew.

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Preventing powdery mildew in Spaghetti Squash

Space plants adequately for air flow. Avoid overhead watering. Do not over-fertilise with nitrogen. Water in the morning so foliage dries before evening.

Other Spaghetti Squash problems

Powdery Mildew in Spaghetti Squash — Causes & Treatment | GreenScout