White spots on plant leaves are a common problem in plant care. They can be caused by various factors such as fungal infections, pests, mineral deficiencies, or environmental conditions . While some spots are harmless, others can indicate serious problems affecting the plant's health.
Causes of white spots on plants
Fungal infections (powdery mildew & downy mildew)
One of the most common causes of white spots on plants is powdery mildew . This fungal disease forms a white, powdery coating on the leaves. Downy mildew, on the other hand, is characterized by white to yellowish spots on the upper side of the leaves and a gray to purple fungal growth on the underside.
Identifying features:
- White, powdery coating on the leaf surface (powdery mildew).
- White or yellowish spots on the leaves, often with a darker underside (downy mildew).
- Leaves curl up or dry out.
Treatment:
- Remove leaves: Cut off heavily infested leaves immediately.
- Improve air circulation: Good ventilation helps reduce moisture on the leaves.
- Natural remedies: Spray with a mixture of milk and water (1:9) or a baking soda solution.
- Fungicides: In case of severe infestation, special agents against powdery mildew are necessary.
Pests ( spider mites , thrips , mealybugs)
White spots on leaves can also be caused by pests . Spider mites leave fine, light spots as they suck the sap from the leaves. Thrips cause silvery, speckled spots. Mealybugs, on the other hand, leave behind a sticky, cotton-like residue.
Identifying features:
- Fine, speckled or silvery-white spots on the leaves.
- Net-like structures (spider mites) or white cotton balls (mealybugs).
- Plant grows slower or loses leaves.
Treatment:
- Wash leaves: Clean with lukewarm water or soap solution.
- Promote natural enemies: Ladybugs and predatory mites help against pests.
- Use neem oil or soft soap solution: Effective against many pests.
Sunburn and burns
When plants are suddenly exposed to direct sunlight, white, burnt spots may appear on the leaves. Particularly sensitive plants such as Philodendron , Monstera , or Alocasia are sensitive to strong UV radiation.
Identifying features:
- Large, irregular white spots on the leaf surface.
- Leaves become papery and dry.
- Spots appear particularly on the sun-facing side.
Treatment:
- Place the plant in the shade: Avoid direct midday sun.
- Protect from sunlight: Use shade nets or curtains.
- Slow acclimatization to sunlight: Especially for plants that come from dark environments.
Mineral deficiency (calcium, magnesium or iron deficiency)
Nutrient deficiencies can also cause white spots on the leaves. Calcium deficiencies, in particular, lead to mottled or deformed leaves. Iron and magnesium deficiencies cause light discoloration between the leaf veins.
Identifying features:
- White or yellowish spots, mostly between the leaf veins.
- Growth disorders or deformed leaves.
- Often observed in hydroponics or calcareous irrigation water.
Treatment:
- Use suitable fertilizer: A balanced fertilizer with trace elements helps.
- Check water quality: Water that is too hard can prevent nutrient absorption.
- Use foliar fertilizer with magnesium or iron .
Limescale deposits from irrigation water
Hard, calcareous water can leave white spots on the leaves. These are often harmless, but can impair the plant's appearance.
Identifying features:
- White, powdery deposits on the leaf surface.
- Easy to wipe off, no impact on plant health.
Treatment:
- Spray leaves with soft water: Use rainwater or filtered water.
- Clean with vinegar solution: 1 part vinegar to 10 parts water.
- Descale watering water: By boiling or letting it stand.
Prevention of white spots on plants
- Regular plant inspection: Early detection of diseases and pests makes treatment easier.
- Correct location: Consider lighting conditions and air circulation.
- Healthy nutrient supply: Balanced fertilization prevents deficiencies.
- Use clean water: To avoid limescale stains.
- Natural protective measures: Neem oil, nettle decoction or garlic decoction help prevent pests.
White spots on plant leaves can have many causes—from harmless limescale deposits to fungal infections, sunburn, or pests. Close observation of the plants helps determine the cause and take appropriate action. Preventative measures such as a balanced nutrient supply, the right location, and regular plant inspections help prevent the appearance of white spots.
