Hydrangea macrophylla Magical Blossom White Cottony Spots - Causes & Fixes

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Mealybugs

These small, soft-bodied insects secrete a white, waxy, cottony substance to protect themselves while feeding on the sap of Hydrangea stems and leaf undersides. They often congregate in crevices where new growth meets older foliage.

Very Common

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How to confirm: Inspect the junctions of leaves and stems for tiny, moving insects hidden within the white fluff.

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

2 Apply an organic insecticide spray to the affected areas, ensuring you coat the undersides of leaves and crevices where the white waxy substance is visible.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

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3 Gently wipe away visible cottony clusters with a cotton swab dipped in isopropyl alcohol to kill the insects on contact.

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Cottony Cushion Scale

This scale insect species produces a thick, white, felt-like covering that resembles cotton. As they feed on the Hydrangea's vascular system, they can cause leaves to yellow and stems to weaken.

Common

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How to confirm: Look for small, hard bumps (the actual insect) underneath the white cottony mass on the branches.

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1 Apply an organic insecticide spray to the plant to eliminate the scale insects and their white protective coverings.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Physically remove visible scale clusters from stems and leaves using a soft cloth or cotton swab dipped in rubbing alcohol.

3 Monitor the plant's health and ensure it is not overwatered, as excess moisture can encourage pest issues.

GROWIT Soil Moisture Meter - Blue

Water Meters

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Powdery Mildew

While typically appearing as a fine white dust rather than thick clumps, advanced stages of this fungal disease can look like patches of white fuzz on Hydrangea leaves. It thrives in high humidity and poor air circulation around the foliage.

Common

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How to confirm: Check if the white spots can be rubbed off easily with your finger, which is characteristic of fungal spores.

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1 Apply an organic fungicide to eliminate the fungal spores and prevent the spread of the mildew 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 foliage and reduce humidity by pruning crowded branches and avoiding overhead watering.

3 Remove and dispose of any heavily infected leaves to prevent the fungus from spreading through the plant.

Fiskars 5/8" Bypass Pruning Shears

Cutting Tools

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Azalea/Hydrangea Lace Bug (Egg masses/Exuviae)

Accumulated cast skins (exuviae) or egg masses from certain piercing-sucking insects can accumulate on the undersides of leaves, appearing as white, irregular debris.

Common

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How to confirm: Examine if the white spots are stationary and lack any sign of movement or organic 'fuzziness' when disturbed.

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1 Inspect the undersides of the leaves for active insects or moving larvae and spray the affected areas with an organic insecticide to eliminate egg masses and adult lace bugs.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Gently wipe or prune away the accumulated white debris and cast skins to prevent further pest buildup and improve airflow around the foliage.

3 Ensure the plant is in a well-draining environment and monitor soil moisture to reduce plant stress, making it less susceptible to piercing-sucking pests.