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?
Phormium mealybug is only found on Phormium and like the host plant originates from New Zealand, it is able to survive British winters out of doors. Most other mealybugs found in Britain are dependent on glasshouse conditions. Mealybugs are sap sucking true bugs. They excrete 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.
The mealybugs tend to cluster around the base of leaves. On young plants large populations can cause plants to lack vigour and foliage may die prematurely. Older established plants seem to be more tolerant of this insect and will often survive without obvious damage.
In most cases this insect needs to be tolerated. It 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 populations of Phormium mealybug
- When purchasing a Phormium examine it carefully and reject any that shows signs of mealybug. 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 in Britain
- Consider replacing heavily affected 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
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.