Scale

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White wax scale on citrus

White wax scale on citrus

Scale are another sap sucking insect and come in a very wide range of shapes and colours.  Most are no larger than 1/2cm  and can be found on leaves, stems and branches.  What they have in common is that these small insects produce a protective shell or scale over themselves whilst they suck sap from the plant tissue underneath.  The sap sucking weakens plants particularly if the scale are in large numbers. If left untreated some scale types can actually kill a plant.

They can loosely be divided into hard and soft scale groups. Soft scale types excrete large quantities of “honeydew” which attracts ants and also provides food for sooty mould to develop.  This does not happen with hard scales.

Some scale are extremely good at blending in and it’s often the appearance of sooty mould that tells a gardening there’s a problem.

Plants Attacked
Wide range including: roses, gardenias, citrus, natives, palms, olive trees and more.

Different stages of scale on peperomia leaf

Different stages of scale on peperomia leaf

Organic Control Methods for Scale
At the first sign of scale it’s time to act.  Do not think “Oh it’s only a few” as there will definitely be more to follow!

  • Spray with eco-oil to smother scale and attract natural predators.  Juveniles mainly develop in warmer months and are easier to kill because they haven’t fully developed their protective scale yet. Spraying in Spring and into Summer is especially recommended to target these juveniles.  Dead scale don’t always drop off plants immediately but will brush off easily with your fingernail compared to live ones.
  • Release Luke the scale eating ladybeetle (Chilocorus circumdatus). Luke will feed on a range of scale including: white louse scale, red scale, oleander scale and oriental scale.
  • If practical you can scrape off live scale from stems/branches with a toothbrush or stiff brush.  Be careful to not scrape so hard you damage the plant tissue.  A followup spray with eco-oil is still recommended as there are bound to be some which you’ll miss.

 

Soft brown scale

Soft brown scale

Severe infestation of rose scale

Severe infestation of rose scale

Scale on fig leaf with sooty mould

Scale on fig leaf with sooty mould