Moth orchid 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 Moth orchid (Phalaenopsis), using what its sources say about pests and diseases, humidity and watering and 4 problems recorded for it.
Sources last read 14 September 2026.
Phalaenopsis, also known as moth orchids, is a genus of about seventy species of plants in the family Orchidaceae. Orchids in this genus are monopodial epiphytes or lithophytes with long, coarse roots, short, leafy stems and long-lasting, flat flowers arranged in a flowering stem that often branches near the end. Wikipedia, CC BY-SA 4.0
Native range: Tropical & Subtropical Asia, NE. Australia. Also sold as Moon Orchid, Moon Orchids, Moth Orchids, moth plant, Phalaenopsis Orchid and Phalaenopsis Orchids.
What Moth orchid’s sources say that bears on this
- Pests and diseases
- Can be troubled by greenhouse thrips and other thrips, hemispherical scale and Boisduval scale. Diseases: botrytis blight.NC State Extension · read 13 September 2026Can be troubled by scale insects, aphids and mealybugs. Diseases: usually none. To prevent bacterial rots, keep water out of the centre of the leaf crown.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 11 September 2026
- Watering
- Water orchids in the morning with lukewarm water: set them in a sink and let water run freely through the foliage and potting medium. Let the pot drain fully so the plants are not left sitting in water.NC State Extension · read 13 September 2026Mist the aerial roots regularly, and water once the plant is nearly dry; roots turning pale and silvery show that watering is due.RHS · read 13 September 2026
How this shows up on a Moth orchid
Clusters of small soft insects on the shoot tips and buds: aphids
Aphids gather on the undersides of new leaves and around buds on the moth orchid, leaving honeydew and shed skins behind.
RHS lists aphids among the pests it may attract. Colonies build within days on young shoots, and the honeydew they shed makes the leaves sticky.
Telling it apart: Where they sit. Aphids crowd soft tips and buds; scale sits still on older stems.
RHS · read 13 September 2026Hard, rounded scale on the undersides of the leaves
The moth orchid is sticky to the touch and yellows slowly. Along the veins on the undersides sit small shell-like scales that lift off with a fingernail.
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 2026Silvery streaks with black specks on the leaves: thrips
Silvery flecks and streaks spread over the leaves of the moth orchid, peppered with tiny black dots. Flowers may open marked or misshapen.
NC State Extension lists thrips among the pests it may attract. The black dots are their droppings, and the silver is air where the cell contents were.
Telling it apart: Shake a flower or leaf over white paper. Thrips show as tiny slender insects that move.
NC State Extension · read 13 September 2026Small white woolly insects tucked into the leaf joints
Look into the tightest angles of the crown: white woolly patches there are mealybug colonies, often with a sticky sheen on the leaves below them.
RHS lists mealybugs among the pests it may attract. They feed on sap and shed the excess as sticky honeydew, and a colony tucked into the joints spreads before it is noticed.
Telling it apart: Whether the white comes with stickiness. Mealybugs leave honeydew; dust and mildew do not.
RHS · read 13 September 2026Possible causes, likeliest first for a Moth orchid
Most likely mealybugs
Ranked higher because Moth orchid's recorded problems point this way.
- Small white woolly insects tucked into the leaf joints RHS
Why: Mealybugs are soft insects that cover themselves in white wax, which gives the cottony look.
What to try:
- Move the moth orchid away from other plants.
- Wipe off every insect you can see with a cotton swab dipped in rubbing alcohol, testing a single leaf first.
What would settle it: Touch a tuft with a cotton swab. If a small, pale, oval insect is underneath, it is a mealybug.
Most likely scale insects
Ranked higher because Moth orchid's recorded problems point this way.
- Hard, rounded scale on the undersides of the leaves RHS
Why: Scale insects settle in one place under a hard or waxy shell and feed on sap.
What to try:
- Move the moth orchid 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 moth orchid does not move.
Most likely aphids
Ranked higher because Moth orchid'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.
Less likely for a Moth orchid, still possible
Questions
- What usually causes pests on a Moth orchid?
- For Moth orchid: mealybugs, scale insects and aphids.
- How can I tell which one it is on my Moth orchid?
- 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 Moth orchid's sources say about its pests and diseases?
- NC State Extension: Can be troubled by greenhouse thrips and other thrips, hemispherical scale and Boisduval scale. Diseases: botrytis blight. RHS: Can be troubled by scale insects, aphids and mealybugs. Diseases: usually none. To prevent bacterial rots, keep water out of the centre of the leaf crown.
- What does this look like on a Moth orchid?
- Aphids gather on the undersides of new leaves and around buds on the moth orchid, leaving honeydew and shed skins behind. Telling it apart: Where they sit. Aphids crowd soft tips and buds; scale sits still on older stems.
Other plants that show pests
AlocasiaFine pale speckling on the leaves, then webbing at the tips: spider mites
Aloe veraSticky leaves and immobile shell-like insects on the stems
Areca palmDull, finely mottled fronds and faint webs: spider mites
Arrowhead plantCurled, sticky new leaf blades with green or black insects: aphids
Asparagus fernCurled, sticky new fronds with green or black insects: aphids
Bird's nest fernSticky leaves and immobile shell-like insects on the stems
Something else wrong with the Moth orchid?
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.