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Soft Scale


Soft Scale, Tortoise Scales, Wax Scales, Coccid Scale


by Wim b. CC BY 3.0

A close up of some soft scale insects Coccidae attached to the back of a leaf
Coccidae, or Soft Scale, are sap-sucking plant pests. They're close relatives of Whitefly, Aphids and Armoured Scale insects. Unlike Armoured Scale, Soft Scale feeds by sucking sugary liquids directly from the phloem of plants. In doing so, they produce copious amounts of honeydew, a sticky sweet by-product. Ants will farm Scale Insects for their honeydew, protecting them from predators in return for the sugary treat. The ants will physically move the Scale so they can exploit new parts of the plant, so they can sometimes worsen infestations. Other symptoms include leaves yellowing and falling from plants early. Honeydew may encourage the growth of black sooty moulds, too.
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Suck the sap from ornamental plants.
Scale are food for ladybugs and other insects.


Adults: Their shape and colour can be variable. Nonetheless, they all produce similar symptoms in the plants they infest. They roughly measure 0.5-1cm. Sometimes they're covered in a waxy secretion which protects them from environmental stressors. They can have spots or markings around the protective shell. Nymphs: Upon hatching, they are mobile and small in size. They crawl across the plant surfaces in desperate search of food! They latch to a particular spot and begin to feed.


For heavy infestations, you may notice the leaves yellowing and falling prematurely. A clear and sticky substance may be found covering the surfaces of leaves and bark, this is called honeydew. Ant activity may increase and worsen the infestation. Growth may be stunted or distorted. Honeydew can result in the growth of black mould, which may conceal the scale from sight.












Biological treatment

It's thought that older, more established plants can tolerate infestations. Regularly tending to plants and practising good housekeeping in the garden will give plants a better chance at survival. Badly infested branches may be pruned and removed and disposed of sensibly. Lighter infestations may be rubbed or picked off with hands. Alcohol-soaked cotton and neem-based leaf shine may be rubbed over the surfaces of the areas infested. Initially, target the main points of infestation (70% of solution) and give a light coating to the whole plant (if small enough). From then on, spot treat plants every day. Capturing natural enemies and releasing them on the affected area may improve infestations. These include insects like ladybirds, hoverflies, lacewing and earwigs. Likewise, by letting parts of the garden 'grow wild' paired with an abundance of pollinator-friendly plants, you can attract the latter into your garden. Insecticidal soaps can be advantageous if applied regularly over several intervals. Use a drop of washing up liquid with a few more drops of vegetable oil, dilute with water. Horticultural oils may be used as the next alternative. They are oil-based and environmentally benign, and these will give some coverage over adult stages. Oils can burn plants in direct sunlight, so read bottle instructions carefully. If ants are also present at the site, these may be providing some protection to the scale. These can be controlled using a product such as Tanglefoot Pest Barrier. This will hopefully present a barrier for the ants that are attempting to reach the scale.

Chemical treatment

Tip: If you choose to use oils, soaps and insecticides; it's always best to apply during peak nymph activity. Most scale insects begin laying eggs when the temperature starts to warm in the spring. It's advised to monitor the pest population until the nymphs are present. Unlike adults, scale nymphs are incredibly active. Often termed crawlers, they run around the surfaces of plants until they have found the perfect site to feed. Here, they continue to grow and develop. It's these earliest stages which are most vulnerable to treatments. Topical pesticides will be ineffective against this pest. Wax Scales are coated with a thick layer of wax which conceals them from environmental stressors. Oils and soaps are thought to be most effective.


Many ornamental plants and crops.
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