Calathea concinna White Powder - Causes & Fixes

Jump to cause: Powdery Mildew Mealybugs Mineral Deposits (Hard Water)

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Powdery Mildew

This fungal disease thrives in the humid environments Calatheas enjoy, especially if there is poor air circulation around the foliage. It manifests as a white, flour-like coating on the leaf surfaces.

Very Common

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How to confirm: Inspect the underside of leaves for fuzzy white patches and check if the plant is placed too close to other dense foliage.

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1 Treat the affected leaves immediately with an organic fungicide to stop the spread of the fungal spores.

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2 Prune and discard any heavily infected leaves to prevent the mildew from spreading to healthy foliage.

3 Improve air circulation around your Calathea by spacing plants further apart or using a small fan, and avoid overhead watering.

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Mealybugs

These sap-sucking insects appear as small, white, cottony masses tucked into the junctions of stems and leaves. They can be mistaken for powder because of their white, waxy coating.

Common

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How to confirm: Use a magnifying glass to check the leaf axils (where the leaf meets the stem) for tiny, moving white clusters.

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1 Isolate the plant immediately to prevent the mealybugs from spreading to your other houseplants.

2 Treat the visible white cottony masses by spraying the plant with an organic insecticide or neem oil spray to kill the insects and their eggs.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

3 Use a cotton swab dipped in isopropyl alcohol to manually remove any remaining mealybug clusters from the stem junctions and leaf undersides.

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Mineral Deposits (Hard Water)

Calatheas are sensitive to salts and minerals in tap water; as water evaporates from the leaf surface, it can leave behind a white, crusty residue.

Common

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How to confirm: Check if the white patches are crispy or scale-like rather than fuzzy, and test your water source for high calcium or magnesium content.

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1 Gently wipe the leaves with a soft, damp cloth using distilled or filtered water to remove the mineral buildup and prevent leaf burn.

2 Switch to using distilled, rainwater, or thoroughly dechlorinated water to prevent future mineral accumulation on the foliage.

3 Monitor the soil moisture levels closely to ensure you aren't overwatering, which can exacerbate mineral salt buildup in the substrate.