Plant Doctor Archive

Pittosporum problems

I'VE bought a new house with a pittosporum hedge that is dropping its leaves badly. It is about 1.5m tall and has black patches on the lower leaves. There are white things about 2mm long that look like scale stuck on the branches. Any advice on giving it a boost?

IT does sound as if scale is the culprit. The black patches on the lower leaves will be sooty mould growing on the sweet honeydew excretions dripping from the scale above.

Pittosporums aren't particularly susceptible to scale but if the hedge is weakened by some other factor, such as drought or lack of nutrients, they could become a problem. I'd be inclined to give the hedge a good trim, cutting back a good two thirds of the leafy growth. This should remove a lot of the scale as they prefer to feed from the soft young stems rather than the tough woody ones. Then spray the remaining growth thoroughly with a relatively user-friendly insecticide such as Clear White Oil or Conqueror Oil. Spray in cloudy weather rather than in bright sunlight, or in the evening, to avoid the risk of scorching the remaining leaves. Apply a dressing of general fertiliser and give the occasional deep watering during dry periods to encourage new growth.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.