scale insects

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.

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.

Biological Control of Soft Scale.

Soft scale can be controlled biologically in greenhouses or conservatories by  Metaphycus  helvolus