Pest Problems Explained - SOFT SCALE INSECT

Scale Insect (Soft Scale) Description

Soft Scale InsectThere are two distinct groups of scale insects - soft scale and hard scale.

The most commonly found soft scales are Coccus hesperidum - the adults are 3-5mm long, green to brown in colour, oval- shaped and appear slightly flattened, and Saisettia coffeae - the adults are 5mm or longer in length, deep brown in colour and dome-shaped.  Most soft scales have 6 legs and can move around the plant as they grow

Hard scales are small pests that also cosume plant juices but have no legs so cannot move.  They secrete a waxy material mixed with waste products as a kind of shell over the top of their body adding to it around the edge on daily basis.  they do not produce any sticky honeydew.  

Scale Insect (Soft Scale) Damage

The symptoms are similar to those of whitefly or aphids.

Soft scales are normally found congregating along leaf veins or stems. The scales feed on plant sap and produce large amounts of sticky honeydew.

Large populations will cause yellowing of the plant and defoliation. The honeydew results in the growth of black sooty moulds which ultimately kill the plant.

Soft Scale Life Cycle

Soft scales produce a number of eggs over several days. The eggs are laid under the cover of the adult "scales" which offer protection during development. The adult dies once it has laid its eggs.

Eggs hatch into "crawlers", which are tiny legged creatures which disperse all over the plant and its foliage in search of a suitable site to settle down and become an immobile scale.

Scales grow relatively slowly and have a long life cycle. Saisettia coffeae takes about 95 days at 18ºC (64ºF) to complete it's life cycle

Hard Scale Life Cycle

There are many species of hard scales and they usually cause severe damage and dieback of infested shoots.  When full grown one can distinguish elongate males that develop into winged insects from the more rounded females.   Females produce eggs underneath the protective scale cover where they remain until hatching.  These crawler stages then spread out over the plant or get carried in the wind to new hosts.  Once settled they moult into legless individuals and start to build their waxy cover.