The adult scales are small insects (Figure 1), about 3 to 4 mm in length, which can be seen by the naked eye. Unlike most other soft scale species, the green coffee scale has well developed legs which enable it to move about the host plant. The nymphs (Figure 1), which are also known as crawlers, develop through multiple instars (stages) and are less than 1 mm in length when first produced. They are oval-shaped and mobile.
Damage: Green coffee scale activity usually occurs on the underside of the leaf (Figure 2) and twigs. However, when infestation levels are high, the scale can be found on the upper leaf surface and on fruit. A useful indicator of activity is the blackening of the upper leaf surface (Figure 3) with sooty mould. Sooty mould is also produced by several other sap-sucking bug species.
A severe infestation of the scale can reduce photosynthesis in the leaves which reduces the vigour and productivity of the host tree. Sooty mould, also formed on the fruit, can increase production costs.