Scale are sap feeding bugs that gradually weaken plants. So called because a colony on the leaf or stem of a plant resembles the scales on a fish. Different colours, often brown but some species are greyish white. Varied in size, anything from 1mm to 6mm. They lead not the most exciting of lives but therein lies their strength. A newly born scale will make a small effort to crawl a few millimetres to find somewhere to live and will then stay put for the rest of its life laying the eggs for the next generation in the same spot. But this immobility and the thickness of their skin makes them resistant to contact insecticides.
Scale Insects are frequently easy to see as the colonies cluster openly on stems but a little less so if they are feeding on the underside of leaves. Infected leaves may be yellow or become otherwise discoloured. Heavily infected plants will gradually lose their vigour. Scale Insects, like other sap feeders, excrete a sugary honeydew which drops onto the foliage below the colony. Such foliage initially develops a sticky sheen but this can rapidly become home to black sooty moulds.
Treatment and control
Spray with a broad spectrum insecticide: Spray decorative, ornamental plants with a systemic insecticide such as BugClear Ultra or BugClear Ultra Gun! (contains acetamiprid). Decorative pot plants can be treated with a drench, for example BugClear Ultra Vine Weevil.