Ceroplastes is a genus of soft scale insect (Coccidae), commonly referred to Wax Scale. They're called Wax Scale after the close resemblance to the melted wax. Their shape is irregular and white in most species. They produce honeydew too, so it's common to see ants when you have a Wax Scale infestation. Ants harvest honeydew from Scale Insects, and in return, the ants protect them from predators and move them to new locations on the plant to feed.
They may reduce the vigour of plants.
Adults: Medium-sized scale insects, no larger than 1cm. Once the adults have found an ideal feeding spot on the host plant, they stay put and continue feeding until they die! These scale insects are shaped irregularly, resembling a melted blob of wax! They are generally white and cream, but some can have streaks of browns and reds. Nymphs: The first instar nymph (1st development stage) resides beneath the leaves of hosts, along the leaf veins specifically. Following the first moult, the second instar nymphs move to the tree bark. They will remain here for the rest of their lives!
Plants 'encrusted' in scales. Small crawling insects (nymphs) on plant surfaces. Honeydew may be seen covering the leaves and stems. Black, sooty moulds on plant surfaces. Plants may loose vigour. It might look like there's melted wax on plants.
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. 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. Use them during cooler parts of the day to avoid burning. 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.
More persistent insecticides should be used as a last resort. These incorporate synthetic pyrethroids and can be more persistent. If a chemical option is sought, check with your local garden centre and please take care to follow the manufacturers' instructions. Check with your local regulating body for guidance on active ingredients and their authorisation for use. Never spray when flowers are present.