Armoured Scale (Diaspididae) is the largest family of scale insects, comprising over 2600 species and 400 genera. They are the best at camouflage. Their shells often mimic the textures of the barks surfaces. They are sap-suckers and unlike Soft Scale, they rupture plant cells directly when feeding. Another key difference to soft scale: these insects possess a tough, waxy shell that covers them. It's not attached to the body, so can be pulled off to reveal the insect inside.
Armoured Scale feed differently to soft scale, so they don't produce any honeydew.
Armoured Scale suck the sap from plants, leading to loss of vigour and leaf wilts.
Armoured Scale look and behave a little differently to Soft Scale. Firstly, Armoured Scale won't produce any honeydew. They can vary in size; some can be as large as 1cm. They can be brown, white, cream, red, black. Sometimes they will store their eggs beneath the shell too. Infestations comprise of females only. Fully mature females are sessile, they will spend the rest of their lives in one place (unless removed by the gardener!). The nymphs are mobile. They're called crawlers. They scuttle across plant surfaces in search of a spot to eat. Tip: The best way of identifying an Armoured Scale is attempting to remove the shell. If armoured, you'll be able to remove the shell and see a small, shiny, soft-bodied insect beneath.
Lighter infestations seem to be tolerated by large, established plants. When infestations are heavy, the plant can begin to lose vigour. Leaves may begin to yellow and may fall early. Branches will appear flaky or scaly in texture.
It's thought that older, more established plants can tolerate light infestations. Regularly tending to plants and practising good housekeeping in the garden will give plants a better chance at survival. Infested branches may be pruned and removed and disposed of sensibly. Tools used should always be sterilised after. 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. 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. 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. Before application, ensure the plant is well hydrated and not in direct sunlight. If so, it might be worth applying oils in the evenings when cooler. Test some oil before applying it to the whole plant. Once applying the primary treatment, continue to spot-treat the scale until they are no more! Please follow treatment instructions carefully, and consult with your garden centre if you're still not confident.
Due to the hard, protective shell these insects possess, it can be challenging to penetrate the outer coating to kill the insect inside. Some neonicotinoids are thought to be effective in controlling Armoured Scale, yet, can be toxic to fish and invertebrates. Always read instructions carefully and check chemicals are authorised for home use. Avoid spraying flowers.