Rosemary 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 Rosemary (Salvia rosmarinus), using what its sources say about pests and diseases and humidity and 4 problems recorded for it.
Sources last read 14 September 2026.
Salvia rosmarinus, synonym Rosmarinus officinalis, commonly known as rosemary, is a shrub with fragrant, evergreen, needle-like leaves and purple or sometimes white, pink, or blue flowers. It is a member of the mint family, Lamiaceae. Wikipedia, CC BY-SA 4.0
Native range: Medit. (temperate). Also sold as Anthos, old man, rose of the sea and southernwood.
What Rosemary’s sources say that bears on this
- Pests and diseases
- Can be troubled by aphids. Diseases: southern blight.NC State Extension · read 13 September 2026Can be troubled by scale insects, tortrix moth, sage leafhopper, cuckoo spit and rosemary beetle. Diseases: foot and root rots, Verticillium wilt, powdery mildews and, rarely, honey fungus.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 Rosemary
Clusters of small soft insects on the shoot tips and buds: aphids
The youngest growth of the rosemary is sticky and distorted, and a closer look finds colonies of small, pear-shaped insects.
NC State Extension 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: Whether you can see them. Aphids are visible to the eye; the mites that distort new growth are not.
NC State Extension · read 13 September 2026Leaves eaten away and webbed together: caterpillars
Chewed leaves on the rosemary come with green or brown caterpillars nearby, often active at night.
RHS lists caterpillars among the pests it may attract. Their damage is chewing, not sucking, so the tissue is gone rather than discolored.
Telling it apart: Droppings. Caterpillars leave dark pellets below the damage; slugs leave slime.
RHS · read 13 September 2026Pale flecks on the leaves and insects that leap away: leafhoppers
The upper surfaces of the leaves of the rosemary carry coarse pale flecks, and white cast skins cling to the undersides.
RHS lists leafhoppers among the pests it may attract. They feed on the undersides and leap off when disturbed, so they are rarely seen at rest.
Telling it apart: Whether the insects jump. Leafhoppers leap; whitefly flies up in a cloud.
RHS · read 13 September 2026Small raised bumps along the stems and veins, with sticky leaves: scale insects
Rows of small, hard scales sit where the veins of the rosemary are thickest, and the surface below them is glossy with honeydew.
RHS lists scale insects among the pests it may attract. Each scale sits in one place drawing sap and dripping honeydew, which is why the leaves below turn sticky.
Telling it apart: Stickiness below the bumps. Scale drips honeydew; a leaf spot is dry.
RHS · read 13 September 2026Possible causes, likeliest first for a Rosemary
Most likely scale insects
Ranked higher because Rosemary's recorded problems point this way.
- Small raised bumps along the stems and veins, with sticky leaves: scale insects RHS
Why: Scale insects settle in one place under a hard or waxy shell and feed on sap.
What to try:
- Move the rosemary 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 rosemary does not move.
Most likely aphids
Ranked higher because Rosemary's recorded problems point this way.
- Clusters of small soft insects on the shoot tips and buds: aphids NC State Extension
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 rosemary 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 Rosemary, still possible
Questions
- What usually causes pests on a Rosemary?
- For Rosemary: scale insects, aphids and spider mites.
- How can I tell which one it is on my Rosemary?
- 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 Rosemary's sources say about its pests and diseases?
- NC State Extension: Can be troubled by aphids. Diseases: southern blight. RHS: Can be troubled by scale insects, tortrix moth, sage leafhopper, cuckoo spit and rosemary beetle. Diseases: foot and root rots, Verticillium wilt, powdery mildews and, rarely, honey fungus.
- What does this look like on a Rosemary?
- The youngest growth of the rosemary is sticky and distorted, and a closer look finds colonies of small, pear-shaped insects. Telling it apart: Whether you can see them. Aphids are visible to the eye; the mites that distort new growth are not.
- Is Rosemary 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
Bigleaf hydrangeaClusters of small soft insects on the shoot tips and buds: aphids
Bird of paradiseDull, finely mottled leaves and faint webs: spider mites
Blue passion flowerPale stippled leaves and tiny moving dots underneath: a mite pest
Something else wrong with the Rosemary?
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.