Hydrangea macrophylla Magical Revolution White Cottony Spots - Causes & Fixes

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Mealybugs

These small, soft-bodied insects secrete a white, waxy, cotton-like substance to protect themselves. In Hydrangea macrophylla, they often congregate at the leaf axils and tender new growth, 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 attached to tiny insects near the stem nodes.

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1 Isolate the plant immediately to prevent the mealybugs from spreading to other greenery in your collection.

2 Apply an organic insecticide spray to the affected areas, ensuring you coat the undersides of leaves and leaf axils where the insects hide.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

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3 Use a cotton swab dipped in isopropyl alcohol to manually remove visible white cottony clusters from tender new growth.

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Cottony Blight (Sclerotinia)

This fungal pathogen produces white, fuzzy mycelium that can appear as cottony patches on stems or leaves, especially in high-humidity environments. It can lead to rapid wilting and stem decay in mophead hydrangeas.

Common

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How to confirm: Inspect the base of the stems for small, dark, nut-like sclerotia embedded in the white mass.

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1 Immediately prune and dispose of all infected stems and leaves to prevent the fungal mycelium from spreading to healthy tissue.

2 Apply an organic fungicide to the affected area to control the spread of the blight and protect remaining healthy foliage.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

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3 Improve air circulation around the plant and reduce humidity by avoiding overhead watering, which helps prevent further fungal development.

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Powdery Mildew

While typically appearing as a fine dust, advanced stages of powdery mildew can look like felted or cottony patches on the leaf surface. It thrives in the humid microclimates often found around large-leaved Hydrangeas.

Common

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How to confirm: Check if the white spots can be wiped off easily with your finger and if they appear more like a film than distinct tufts.

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1 Apply an organic fungicide to the affected leaves to eliminate the powdery mildew spores and prevent further spread.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

2 Improve air circulation around the plant by pruning crowded branches and ensuring the plant is not in a stagnant, overly humid microclimate.

3 Remove and dispose of heavily infected leaves to reduce the fungal load in the immediate area.

Fiskars 5/8" Bypass Pruning Shears

Cutting Tools

$13

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Woolly Aphids

Certain aphid species produce a white, fluffy secretion that resembles cotton. They cluster on the undersides of Hydrangea leaves, causing leaf curling and stunted growth.

Common

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How to confirm: Look for tiny, pear-shaped insects underneath the leaves alongside the white patches.

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shopping_cart Recommended Products

1 Apply an organic insecticide spray to the undersides of the leaves to eliminate the woolly aphid colonies.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Use yellow sticky traps near the plant to capture adult aphids and prevent further infestation.