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Scale

Scale insects (Diapsis, Lepidosaphs and Coccus) come in several forms, and are characterized by small shell-like creatures which move very little, very slowly, sucking the sap of the plant cells and moving to the next one, in a methodical manner. The plant becomes debilitated and eventually may die. When the cells are punctured they exude honeydew which is used by ants. The ants in turn serve the scale by carrying them from plant to plant, spreading them to healthy new hosts. The honeydew is also host to a mould, or fungus, which is black in colour. This sooty mould leaves a black or gray cast on the leaves, which is an indication of sucking insects being present.

Scale may be eradicated by an oil based insecticide which smothers the insect or systemic or organophosphate based poisons.