Mealybugs: how to recognise and treat it

Pest

Symptoms

Fluffy white wax in leaf axils, leaf sheaths, between twining stems and other sheltered spots; the insects or their orange-pink eggs are underneath.
Large colonies weaken the plant, slow its growth and can cause early leaf drop.
Sticky honeydew on leaves and stems, often blackened by sooty mould.
Ants feeding on the honeydew.

On houseplants, dab mealybugs with isopropyl alcohol diluted to 70% or less; test on a small part of the plant first for leaf burn.
Spray insecticidal soap, horticultural oil or neem oil directly on the insects — it works best on young nymphs with little wax; repeat as needed.
In greenhouses, release the mealybug ladybird Cryptolaemus montrouzieri or parasitic wasps; they need warmth and work best from May to September.
Prune out infested parts, and throw away heavily infested plants rather than spraying them again and again.

Contact sprays with lambda-cyhalothrin or deltamethrin on ornamentals, covering the plant thoroughly; the waxy coat makes them hard to hit, they may work little better than soaps or oils, and they kill beneficial insects. Follow the label.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Inspect new plants carefully and keep them apart from your collection for at least a month — mealybugs mostly arrive on new plants.
Avoid excess nitrogen fertiliser, which stimulates the soft new growth where mealybugs lay eggs.
Clear dead leaves and prunings, and check pots and stakes for mealybugs and egg sacs.
Regularly check prone plants — cacti and succulents, orchids, citrus, hoya, African violets and other houseplants.

Figures checked against these sources.