Hydrangea macrophylla Magical Cantate 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. On Hydrangea macrophylla, they often congregate at the leaf axils and stem nodes, sucking sap and causing leaf yellowing.

Very Common

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How to confirm: Use a magnifying glass to check if the white spots move or are attached to the stem joints.

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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.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

3 For heavy infestations, use a targeted spray to ensure the solution reaches the leaf axils and stem nodes where pests congregate.

Chapin 20004 1-Gallon Pump Sprayer

3.8 L • Polyethylene

$15

In Stock

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Cottony Scale

Similar to mealybugs, scale insects produce a white filamentous coating. In Hydrangeas, this can lead to stunted growth and the secretion of honeydew, which may trigger sooty mold growth on the leaves.

Common

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How to confirm: Check for small, brownish bumps underneath the white waxy mass on the stems.

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1 Treat the plant with an organic insecticide/miticide spray to eliminate the scale insects and their white protective coating.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Physically remove visible scale insects from stems and leaves using a cotton swab dipped in isopropyl alcohol.

3 Clean the surrounding foliage and leaves to remove honeydew residue and prevent the secondary growth of sooty mold.

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Powdery Mildew (Early Stage/Fungal)

While typically appearing as a fine dust, certain fungal outbreaks can look like fuzzy patches. In humid conditions, this fungus thrives on the large surface area of Hydrangea macrophylla leaves.

Common

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How to confirm: Rub the white spot with your finger; if it wipes off easily like dust rather than looking like a clump, it is likely fungal.

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1 Apply an organic fungicide to the affected leaves to stop the spread of the fungal spores.

Bonide Captain Jack's Copper Fungicide 32 oz

0.9 L • 1 pcs • Organic

$12

In Stock

2 Improve air circulation around the plant and avoid overhead watering to reduce the humidity that fuels powdery mildew.

3 Prune and dispose of any heavily infected leaves to prevent the fungus from spreading to healthy foliage.

Fiskars 5/8" Bypass Pruning Shears

Cutting Tools

$13

In Stock

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Woolly Aphids

These aphids produce a white, flocculent secretion that gives the plant a 'cottony' appearance. They are particularly attracted to the tender new growth of many hydrangea cultivars.

Common

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How to confirm: Look for clusters of tiny insects on the undersides of new, soft leaves.

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shopping_cart Recommended Products

1 Apply an organic insecticide spray to the affected new growth to eliminate the woolly aphids and their white secretions.

Bonide Captain Jack's Neem Oil 32 oz

0.9 L • 1 pcs • Organic

$10

In Stock

2 Inspect the undersides of leaves and stems regularly to catch any remaining pests before they spread.

3 Prune away heavily infested stems to prevent the aphids from spreading to the rest of the hydrangea.