Advice
RHS Help & Advice
Phormium mealybug (Balanococcus diminutus)
Plants affected
New Zealand flax (Phormium) species and cultivars.
Symptoms
Flattened, soft-bodied insects, up to 5mm long and covered with greyish white mealy wax, form colonies on the basal areas of the upper leaf surface of New Zealand flax (Phormium). Heavy infestations can cause unhealthy growth, yellowing foliage and eventually the death of the plant.
Cause
This mealybug, like the phormiums they infest, originates from New Zealand, and was inadvertently brought into Britain on imported plants during the 1970s. Unlike the mealybugs encountered in greenhouses and on houseplants, the phormium mealybug is hardy enough to survive harsh winters out of doors.
Control
Insecticides have little effect because the mealybugs are concealed between the tightly folded leaf bases.
Destroy badly infested plants. Before buying phormiums, examine the leaf bases carefully and reject any that show signs of mealybugs or their waxy secretions. Mealybugs cannot fly and so uninfested plants are likely to remain in that condition unless they are planted in close proximity to other phormiums that have this pest.