Scale (botany)

Scale is a type of pest insect that attatches to plants and sucks plant fluids for nutrition. It coats itself with a covering (hence scale) that makes it quite resistant to pesticides, which must be used only in the juvenile crawler stage, if it is to be effective. Scale, however can be controlled with horticultural oil, which suffocates them, or by biological controls.

Cottony Cushion Scale: the pest that launched a pest control revolution with photos