Geranium macrorrhizum White Cottony Spots - Causes & Fixes

Jump to cause: Mealybugs Powdery Mildew Cottony Blight (Botrytis cinerea)

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Mealybugs

These small insects secrete a white, waxy, cotton-like substance to protect themselves. They congregate in the crevices of the Geranium macrorrhizum leaves and stems, sucking sap and weakening the plant.

Very Common

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How to confirm: Use a magnifying glass to check if the white spots move or are clustered near stem nodes.

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

2 Treat the infestation by spraying the plant with an organic insecticide/miticide to kill the insects and remove the waxy coating.

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3 Gently wipe away visible white cottony clusters from stems and leaf crevices using a cotton swab dipped in isopropyl alcohol.

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Powdery Mildew

A common fungal disease in Geranium species, it presents as white, flour-like patches on leaf surfaces. It thrives in humid conditions with poor air circulation around the foliage.

Very Common

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How to confirm: Check if the white spots look like a fine dusting of flour that can be rubbed off with your finger.

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1 Apply an organic fungicide to eliminate existing fungal spores and prevent the spread to healthy leaves.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

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2 Improve air circulation around the plant by pruning crowded foliage and ensuring the plant is not in a high-humidity pocket.

3 Avoid overhead watering to keep the leaf surfaces dry, as moisture on leaves encourages mildew growth.

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Cottony Blight (Botrytis cinerea)

This fungus can cause gray or white fuzzy growth, particularly on aging petals or decaying organic matter near the base of the plant. It often appears during periods of high moisture and low temperatures.

Common

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How to confirm: Inspect if the white patches are accompanied by soft, decaying, or brownish tissue on the flowers or leaves.

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shopping_cart Recommended Products

1 Prune and remove all infected plant material, including decaying organic matter at the base, to prevent the fungus from spreading.

2 Apply an organic fungicide to treat the remaining healthy tissue and protect against further fungal development.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

3 Improve air circulation around the plant and avoid overhead watering to reduce the high moisture levels that trigger Botrytis.