Scale Insects

Settled scale insects appear as small, often circular or oval bumps on bark, twigs, leaves, or fruit, and can be mistaken for plant tissue at first glance. Armoured scales have a hard, detachable waxy shield that can be lifted with a fingernail to reveal the insect beneath; soft scales have a waxy covering fused to the body and typically produce honeydew.

Because soft scales excrete honeydew, sooty mould is a common associated sign, whereas armoured scales, which do not produce significant honeydew, are more often noticed through bark or leaf discolouration around feeding sites.

Eggs are laid beneath the female’s covering, and the newly hatched crawlers are the only mobile stage, walking or being carried by wind, animals, or equipment to new feeding sites before settling and losing most of their mobility. Several generations can occur per year in warm climates.

Sustained feeding by dense colonies can cause twig and branch dieback, leaf yellowing and drop, reduced fruit quality, and general loss of vigour, with soft-scale honeydew adding sooty mould that further reduces photosynthesis and fruit marketability.

Host crops include orange, olive, tea, and mango, along with many other perennial fruit, plantation, and ornamental crops.

Inspecting bark, twigs, and leaf undersides for settled scales, checking for honeydew and sooty mould, and tracking crawler emergence with sticky tape or double-sided tape bands help time monitoring to the brief, vulnerable crawler stage.

Because settled scales are protected under their covering, management emphasises the crawler stage and conservation of natural enemies within an integrated approach.

• Conserve parasitoid wasps, predatory beetles, and lacewings
• Prune out heavily infested twigs and branches where practical
• Time any intervention to the crawler stage, when insects are unprotected and mobile
• Inspect and avoid moving heavily infested planting material between sites