Scale Insects or simply scales are small, brown discs attached to the underside of leaves and on the stem.
They are covered with an outer waxy shell which protect them from chemical penetration.
A heavy infestation by Scale Insects may cause yellowing of the leaves and produces a sticky honeydew which is a fertile ground for black sooty mold.
1.Remove heavily infested parts of the houseplant and destroy to prevent further spread.
2.A light infestation by Scale Insects can be dealt with by wiping them off with a cotton bud dabbed with a solution of 4 parts water and 1 part rubbing alcohol followed by thorough spraying of the plant with the solution. Repeat as necessary.
3.A severe infestation may be difficult to eradicate but can be dealt with by weekly application of a systemic insecticide as per the manufacturer's recommendations.