Scale - general









Three types of scale are a major concern of food crops. These are soft scale (family Coccidae), armoured scale (family Diaspididae) and mealybugs (family Psuedococcidae). Two other families have species which we also encounter are: Margarodidae – cottony cushion scale and Eriococcidae- felt scale All scale have some sort of waxy, protective covering over their bodies and usually live in colonies. Armoured refers to the hard waxy shell that this type of scale bug produce. These scale are usually smaller than soft scale. The shell can be made up of discarded moults, bits of the host plant and other materials which make it very tough. The shell is not discarded when the scale moults but added to with a larger covering allowing for the growth of the scale, forming concentric layers. The shell is not attached to their bodies; it protects the scale like a suit of armour. The armoured scale do not excrete honeydew and therefore will not have ants over the plant. Species include: Oleander scale (Aspidiotus nerii) – citrus, grape, macadamia, olive, oleander, orchid, persimmon White louse scale (Unaspis citri)- mainly on citrus Rose scale (Aulacaspis rosae)- blackberry, loganberry, raspberry, rose Red scale (Aonidielia aurantii) –citrus, olive, passionfruit, squash Soft-bodied scale, as their name suggests, produce a soft, thin waxy coating over their bodies which cannot be separated from them. They can be a variety of shapes and colours-flat, oval, domed, pink, black, brown, and white. These scale will produce honeydew, which in turn creates sooty mould. Species include: magnolia scale (Neolicanium cornuparvum) Pink wax scale (Ceroplastes rubens)- coffee, avocado, banana, citrus, mango, custard, apple Black scale (Saissetia oleae)- apple, apricot, citrus, fig, olive, passionfruit, pear plum quince (Parasaissetia nigra)- avocado, citrus, fig, guava, ginger, hibiscus, mango White scale (Ceroplastes destructor)- avocado, citrus, coffee, guava, hibiscus, persimmon, stone fruit, rosemary The adult females, with the exception of the mealy bug, are virtually always immobile, living their entire lives attached to the host plant under their protective covers. In most species the males, which look like small wasps, will have wings, but do not feed or live for very long. The young, called crawlers, can move about in search of a place to feed and build their protective coverings when mature. They can also be dispersed by the wind. Mealybugs are a type of scale but females keep their legs and are able to move around.

Adult size: 1-5 mm

Out and about

Found all year round in warmer areas and greenhouses, but most numerous in summer after the eggs laid in spring have hatched. At this time of year the new growth on plants would be very enticing. They like dry, warm habitats with thousands of species worldwide. Australia has hundreds of species occurring mainly in eastern Australia particularly in the subtropical and temperate regions.

Reproduction and Life cycle

Scale insects can hatch from eggs or be born live without the female needing to mate. Usually, the eggs hatch in spring and once the crawlers have found a good spot they will stay there for most of the summer. The female can lay more than one hundred and fifty eggs in a season. The nymphs go through three instars. The males pupate into flying adults that look like small wasps. Their sole purpose is to mate, and they manage to do this through the females’ scale covering. In greenhouses and warmer regions they will breed all year round but in cooler areas they may only have one or two generations over summer. Mealy bugs reproduce very quickly. Females of some species are able to produce live young whilst others will lay up to 100 eggs.

To deter

To control

Sprays are particularly effective on the young crawlers before they have developed their waxy coatings - Soapy water spray - White oil spray - Neem oil spray - Spray tea of garlic, nettles, basil or wormwood - Spray pyrethrum if infestation is bad, but this will also harm beneficial insects If ants are protecting them, sprinkle diatomaceous earth around the base of the plant. See the information on ants for other methods of dealing with them.

Plants to repel

Plants to attract


Lacewings / Lady beetles / Minute pirate bug / Parasitoid wasps
Why they are a Pest
Scale are small, sap-sucking parasites related to aphids and mealy bugs. Most live in colonies and attack a wide range of plants though many are host specific. They can severely affect the growth of the plant, weakening it and distorting the new growth. Heavy infestations can severely affect the health of the plant. As with aphids, soft scale secrete honey dew which attracts ants. The ants protect and “farm” the scale bugs, moving them to different places over the plant and in some instances taking eggs back to their nest over winter and bringing them out in spring to hatch. If there is no sooty mould over the leaves, then the scale will be the amoured variety. The honeydew itself can grow sooty mould (a fungus), which will not kill the plant but does inhibit photosynthesis. It can be treated with a soap spray, white oil or neem spray.