The hemispherical or helmet scale, Saissetia coffeae, occurs widely in tropical regions and in greenhouses throughout the world. It is a severe pest in coffee and citrus. Many ornamental crops can also be affected, including various different species of fern, orchid, ficus, oleander and carnation.
Life cycle and appearance of Hemispherical scale
An adult female of S. coffeae has a hemispherical form with a smooth surface. The colour is usually dark to sometimes lighter brown or almost yellow, with many evenly distributed light yellow flecks. The high, rounded form and smooth surface distinguish the species from most other soft scales. The size depends on the host plant and can vary from 2 to 4.5 mm.
The young nymphs are white to yellowish, more oval in form and with a raised H-pattern on the dorsal surface. All instars live on the underside of leaves, often close to the midrib. Only when an infestation is particularly severe do individual scales appear on stems, branches and twigs.
The scales present are usually quite easy to see as shiny brown domes on leaf undersides close to the midribs. They produce large amounts of honeydew causing build-up of sticky deposits on nearby surfaces. The honeydew may attract attendant ants and sooty moulds grow on the sugary deposits. Badly fouled leaves may drop prematurely.