Plant Diseases Coccidae, black soft scale.

Finally, I manage to identify the insects infesting our trees. It is the Scale insects, Coccidae family.

The insects in this family are covered with wax secretion. The covering may be scale-like or mussel-shaped. From their appearance they do not look like insect. When they grow, most of their external organs, such as their legs, wings and antenna, are reduced and become functionless.

The young scale insects have three pair of legs, known as 'crawlers'. It is their responsibility for spreading and looking for suitable place to start new colony. They are very small, although they have no wings, they can spread by wind borne. When the females settle, they seldom move. Male adult scale insects are winged.

They affect different type of board leaf plants. The insects live under the protected shell cover, which is their waxy secretion. Notice the sooty mould that they induced. The insects suck the plant juice. Within the juice, there are water and sugar more than the insects need. They are excreted as honeydew. This induces the mould and attracts ants. The adults are well under protection. Some ladybirds are the predators of their young.


This infection, when prolonged shall reach a stage the it kills the plant. We had tried removing the insects manually to about 90% and find the the plant's growth rate is back to normal. We are testing for an easier / faster way to remove these.