Phormium mealybug

Phormium mealybug unlike the glasshouse mealybugs, only affects New Zealand flax and can survive out of doors throughout the year.

Phormium mealybug

Phormium mealybug

Quick facts

Common name Phormium mealybug
Scientific name Balanococcus diminutus
Plants affected New Zealand flax, Phormium
Main symptoms Fluffy white wax, honeydew and sooty moulds
Most active Year round

What is phormium mealybug?

Like the host plant, phormium mealybug originates from New Zealand and is able to survive British winters out of doors. Most other mealybugs found in Britain which are dependent on glasshouse conditions. Mealybugs suck sap from plants and excrete the excess sugars as honeydew. This lands on the leaves and stems were it is often colonised by sooty moulds, giving the surfaces a blackened appearance.

Phormium mealybug is specific to Phormium and can prove damaging, particularly on young plants. The insects tend to cluster around the base of the leaves and heavy infestations cause plants to lack vigour and the foliage may die prematurely. Older established plants seem to be more tolerant of this insect and will often survive without much obvious damage.


This is a very difficult insect to control as the mealybugs are concealed at the base of leaves or where leaf margins are folded together. This makes it very difficult to reach them with a pesticide and none of the products currently available to home gardeners is likely to give effective control.

  • Established plants can tolerate light infestations of Phormium mealybug
  • When purchasing a Phormium examine it carefully and reject any that shows signs of mealybug infestation. A plant free of mealybug is likely to remain in that condition as this insect cannot fly and there is little opportunity for it to spread from other gardens
  • Consider replacing heavily infested plants
  • The biological controls for available for glasshouse mealybugs are unlikely to control phormium mealybug as they require the warmer temperatures in glasshouses to be effective

Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.