Organic scale control.

Scale insects can do a lot of damage to plants. They are sometimes not noticed until the infestation is quite bad.

They are sap-suckers and will take the life away from plants, slowly but steadily killing it if the pests are on there too long.
The tiny insect creates a waxy outer covering to protect itself. Adults don't move. The young crawl away to a spot where they settle in and form their own scale.

There are soft and hard-bodied scales, which need different approaches to control.

Soft scale are easily killed by spraying organic eco-oil or white oil all over the pests on the leaves. This kills them fairly quickly. The oil covers the insects and suffocates them. It's not harmful to beneficial insects.

They can also be removed with an old toothbrush or dish brush. Give the stems a good scrub with soapy water and they will go easily.

White wax scale are larger and their cases are thicker. Oils may not sufficiently penetrate to suffocate the pests. A repeat spray after two weeks or so should finish them off.
Painting turpentine onto them will also kill them.

There are some tiny parasitoid wasps that will sometimes lay their eggs inside scale. Wasps are important bio control for many insect pests.
Hoverfly, lacewing and ladybird larvae also eat some scale.

Controlling ants near plants susceptible to scale can help as ants 'farm' scale, carrying them around to plants, where they produce sweet honeydew in their wastes. It is a rich food for ants.

So, if you see scale on your citrus or rose, don't panic, just get rid of it and your plant will be happy again.