Mealybugs: identify the wax, honeydew and hidden colonies

Mealybugs are small sap-feeding insects which shelter where leaves meet stems, beneath foliage and around roots. A colony looks like separate oval insects dusted in white wax, often surrounded by fluffier egg material. On citrus, succulents and patio ornamentals, they can remain unnoticed until sticky leaves or black sooty mould make the infestation obvious.

The wax is protective, not a fungus. Adults and young stages insert their mouthparts into plant tissue and excrete sugary honeydew. Sooty-mould fungi grow on that deposit, coating a leaf without invading it. Ants visiting the honeydew are therefore a useful warning sign, although they do not prove which sap-feeder is present.

Where to inspect

• leaf joints, tight branch forks and the underside of curled leaves
• beneath loose bark, plant labels and the rims of containers
• around citrus fruit stalks and dense flower clusters
• at drainage holes or in the root ball when a plant declines without visible insects

Scale insects, whitefly and woolly aphids can produce related symptoms. A hand lens helps: mealybugs are soft-bodied and segmented beneath their powdery coating, while many scale insects form a fixed shell.

Start with containment

Move an affected pot away from neighbouring plants. For a light, accessible colony, wipe insects away carefully or prune a heavily occupied shoot. Repeat inspections matter because eggs and sheltered individuals may remain. Wash honeydew from robust leaves with plain water so that fresh deposits become visible.

Good airflow and sensible nitrogen feeding make dense, soft growth less inviting, but hygiene alone will not clear an established colony. Natural predators can suppress outdoor populations, so broad-spectrum spraying may make control harder by killing the insects that feed on mealybugs.

Using a plant-protection product

Authorised uses vary by crop, setting and country. Before treating, identify whether the plant is edible or ornamental, whether it is indoors or outdoors and which life stage is exposed. Obtain current Spanish label advice from an appropriate retailer or plant-health authority. Covering a plant repeatedly with household mixtures is not a safe substitute for a labelled use, particularly on citrus fruit or in hot sun.

Sources and review

This guide was reviewed in August 2026 using the Royal Horticultural Society guide to mealybugs and the Spanish Ministry of Agriculture register of authorised plant-protection products.