Polka dot begonia 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 Polka dot begonia (Begonia maculata), using what its sources say about pests and diseases, humidity and watering and 5 problems recorded for it.
Sources last read 14 September 2026.
Begonia maculata, the polka dot begonia, is a species of begonia native to southeast Brazil. It grows naturally in the understory of the Atlantic rainforest, with occurrences confirmed in the Brazilian states of Espírito Santo and Rio de Janeiro. Wikipedia, CC BY-SA 4.0
Native range: Brazil (Rio de Janeiro) (wet tropical). Also sold as trout begonia.
What Polka dot begonia’s sources say that bears on this
- Pests and diseases
- Can be troubled by aphids, vine weevil, greenhouse thrips, mites, mealybugs and caterpillars. Diseases: rhizome rot, stem rot, powdery mildews and grey moulds.RHS · read 13 September 2026
- Humidity
- ASHRAE recommends indoor relative humidity between 30% and 60%Penn State Extension · read 13 September 2026
- Watering
- Does not cope with constant direct sun or with waterlogging. During growth, water moderately and give a balanced liquid fertiliser at every other watering.RHS · read 13 September 2026
How this shows up on a Polka dot begonia
Irregular notches bitten from leaf edges by an insect pest
Irregular notches appear along the edges of the leaf blades of the polka dot begonia, bitten at night by adult weevils; later the plant may wilt as grubs eat the roots.
RHS lists vine weevil among the pests it may attract. The adults notch the leaves, and their grubs feed on roots in containers through autumn and winter.
Telling it apart: The shape of the damage. Weevils bite notches from the edge; caterpillars eat holes anywhere.
RHS · read 13 September 2026Leaves eaten away and webbed together: caterpillars
Chewed leaf blades on the polka dot begonia 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: Holes or notches. Caterpillars eat through the leaf; vine weevil adults bite notches from the edge.
RHS · read 13 September 2026Silver-flecked leaves and marked or distorted flowers: an insect pest
Silvery flecks and streaks spread over the leaf blades of the polka dot begonia, peppered with tiny black dots. Flowers may open marked or misshapen.
RHS lists thrips among the pests it may attract. They feed on leaves and in flowers, and hide in buds, which makes them hard to spot.
Telling it apart: Whether the marks are silver. Thrips leave a sheen; sun scorch leaves dry, bleached tissue.
RHS · read 13 September 2026Sticky buds and shoot tips crowded with small insects
Aphids gather on the undersides of new leaf blades and around buds on the polka dot begonia, leaving honeydew and shed skins behind.
RHS lists aphids among the pests it may attract. They feed on the sap of soft new growth, which distorts it, and they multiply quickly without mating.
Telling it apart: Whether you can see them. Aphids are visible to the eye; the mites that distort new growth are not.
RHS · read 13 September 2026White, cottony tufts in the joints of the leaf blades: mealybugs
Clusters of white wax sit where each leaf blade joins the stem and along the undersides of the polka dot begonia. Lifted with a cotton swab, each tuft holds a soft, pale insect, and the leaf blades below are sticky.
RHS lists mealybugs among the pests it may attract. The wax keeps them dry and hard to reach, so they multiply in the sheltered joints of the vine.
Telling it apart: Where the white is. Mealybugs gather in joints and under leaves; a powdery coating across the top of a leaf is mildew.
RHS · read 13 September 2026Possible causes, likeliest first for a Polka dot begonia
Most likely mealybugs
Ranked higher because Polka dot begonia's recorded problems point this way.
- White, cottony tufts in the joints of the leaf blades: mealybugs RHS
Why: Mealybugs are soft insects that cover themselves in white wax, which gives the cottony look.
What to try:
- Move the polka dot begonia 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 aphids
Ranked higher because Polka dot begonia's recorded problems point this way.
- Sticky buds and shoot tips crowded with small insects 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 polka dot begonia 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 Polka dot begonia, still possible
Questions
- What usually causes pests on a Polka dot begonia?
- For Polka dot begonia: mealybugs, aphids and spider mites.
- How can I tell which one it is on my Polka dot begonia?
- 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 Polka dot begonia's sources say about its pests and diseases?
- RHS: Can be troubled by aphids, vine weevil, greenhouse thrips, mites, mealybugs and caterpillars. Diseases: rhizome rot, stem rot, powdery mildews and grey moulds.
- What does this look like on a Polka dot begonia?
- Irregular notches appear along the edges of the leaf blades of the polka dot begonia, bitten at night by adult weevils; later the plant may wilt as grubs eat the roots. Telling it apart: The shape of the damage. Weevils bite notches from the edge; caterpillars eat holes anywhere.
- Is Polka dot begonia safe to handle while I check it?
- Its sources list it as toxic to cats and dogs. Wash your hands after handling the roots or sap, and keep trimmings away from pets.
Other plants that show pests
Rex begoniaClusters of small soft insects on the shoot tips and buds: aphids
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
Something else wrong with the Polka dot begonia?
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.