Bigleaf hydrangea pests, webbing or sticky leaves: causes and what to do
6 results in the diagnosis tree begin with pests, 5 of them marked likely when the answers fit. They are ordered here for Bigleaf hydrangea (Hydrangea macrophylla), using what its sources say about pests and diseases and humidity and 3 problems recorded for it.
Sources last read 14 September 2026.
Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native and endemic to Japan. 5 m (8 ft) or more broad with large heads of pink or blue flowers in summer and autumn. Wikipedia, CC BY-SA 4.0
Native range: SC. Japan (to Izu Ōshima), Kazan Rettō (temperate). Also sold as French Hydrangea, Hortensia, Lacecap Hydrangea, Mop-head Hydrangea, mophead hydrangea and penny mac.
What Bigleaf hydrangea’s sources say that bears on this
- Pests and diseases
- Can be troubled by vine weevil, hydrangea scale, capsid bug and aphids. Diseases: honey fungus, powdery mildews, grey moulds and a leaf spot can occur.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 13 September 2026
How this shows up on a Bigleaf hydrangea
Clusters of small soft insects on the shoot tips and buds: aphids
The youngest growth of the bigleaf hydrangea is sticky and distorted, and a closer look finds colonies of small, pear-shaped insects.
RHS lists aphids among the pests it may attract. They favor tender tips and buds, so the damage concentrates where the plant is growing.
Telling it apart: Where they sit. Aphids crowd soft tips and buds; scale sits still on older stems.
RHS · read 13 September 2026Irregular notches bitten from leaf edges by an insect pest
The plant rocks loose in its pot and droops, and the root ball holds curled white grubs among chewed roots.
RHS lists vine weevil among the pests it may attract. Grubs hatch in the potting mix and eat the roots out of sight, so a plant in a pot can collapse with little warning.
Telling it apart: Whether the plant is loose. Grub damage leaves a plant that lifts from its pot with few roots.
RHS · read 13 September 2026Sticky leaves and immobile shell-like insects on the stems
Rows of small, hard scales sit where the veins of the bigleaf hydrangea are thickest, and the surface below them is glossy with honeydew.
RHS lists scale insects among the pests it may attract. The insect settles under a waxy shell and feeds on sap for life, so a colony builds quietly along the stems.
Telling it apart: Whether the bumps sit on the veins. Scale follows the sap; spots from disease scatter across the leaf.
RHS · read 13 September 2026Possible causes, likeliest first for a Bigleaf hydrangea
Most likely scale insects
Ranked higher because Bigleaf hydrangea's recorded problems point this way.
- Sticky leaves and immobile shell-like insects on the stems RHS
Why: Scale insects settle in one place under a hard or waxy shell and feed on sap.
What to try:
- Move the bigleaf hydrangea away from other plants.
- Scrape the scales off with a fingernail or a soft brush, then wipe the stems and leaves.
What would settle it: Push a bump gently with a fingernail. Scale comes away and leaves a mark; a bump that is part of the bigleaf hydrangea does not move.
Most likely aphids
Ranked higher because Bigleaf hydrangea's recorded problems point this way.
- Clusters of small soft insects on the shoot tips and buds: aphids RHS
Why: Aphids cluster on soft new growth and flower buds, where the sap is easiest to reach.
What to try:
- Rub them off with fingers, or rinse them off in a sink or shower.
- Repeat every few days while new ones appear.
What would settle it: Look for the pale shed skins among the insects. Aphids molt as they grow, and the skins are left behind in the colony.
Most likely spider mites
Why: Spider mites feed on individual leaf cells, and each emptied cell shows as a pale speck.
What to try:
- Move the bigleaf hydrangea away from other plants.
- Wash the leaves, top and underside, with a strong spray of water in a shower or sink.
What would settle it: Hold a sheet of white paper under a leaf and tap the leaf. Tiny specks that move across the paper are mites.
Less likely for a Bigleaf hydrangea, still possible
Questions
- What usually causes pests on a Bigleaf hydrangea?
- For Bigleaf hydrangea: scale insects, aphids and spider mites.
- How can I tell which one it is on my Bigleaf hydrangea?
- What can you see? Fine webbing, and tiny pale speckles on the leaves; White, cottony tufts in the leaf joints; Small brown or pale bumps on stems and leaves that do not move; Clusters of small, soft insects on the new growth; Tiny dark flies around the soil; Sticky, shiny residue, but no insect I can see.
- What do Bigleaf hydrangea's sources say about its pests and diseases?
- RHS: Can be troubled by vine weevil, hydrangea scale, capsid bug and aphids. Diseases: honey fungus, powdery mildews, grey moulds and a leaf spot can occur.
- What does this look like on a Bigleaf hydrangea?
- The youngest growth of the bigleaf hydrangea is sticky and distorted, and a closer look finds colonies of small, pear-shaped insects. Telling it apart: Where they sit. Aphids crowd soft tips and buds; scale sits still on older stems.
- Is Bigleaf hydrangea safe to handle while I check it?
- Its sources list it as toxic to people. Wash your hands after handling the roots or sap, and keep trimmings away from pets.
Other plants that show pests
African violetIrregular notches bitten from leaf edges by an insect pest
Barberton daisyCurled, sticky new leaves with green or black insects: aphids
Bearded irisRagged holes and slime trails: a slug or snail pest
Bird of paradiseDull, finely mottled leaves and faint webs: spider mites
Blue passion flowerPale stippled leaves and tiny moving dots underneath: a mite pest
Bush lilySmall white woolly insects tucked into the leaf joints
Something else wrong with the Bigleaf hydrangea?
What this does not cover
This page orders a decision tree's results using a plant's sourced care. It has not seen your plant, its pot or its window, and two problems at once are common: that is the usual reason a confident answer turns out wrong. The questions in the diagnosis tool narrow it further than a list can.