When buying Citrus, Acacia or Choisya, check carefully to make sure they are free of infestation. If plants do become infested, this can be a difficult pest to eradicate. On small plants, look for and remove the scales and their egg mounds before eggs hatch.
In many parts of the world, an Australian ladybird known as the vedalia ladybird, Rodolia cardinalis, has been released as a biological control for fluted scale. This ladybird is not commercially available in the UK but it has been found in some London gardens. It probably arrived accidentally, along with the scale insect, on imported plants.
Plants that are small enough to be sprayed can be treated with deltamethrin (e.g. Bayer Sprayday Greenfly Killer), lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) or the neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra). On citrus plants where the fruits are going to be eaten, only organic insecticides, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit and Veg, Defenders Bug Killer), plant oils (e.g. BugClear for Fruit & Veg Gun!) or fatty acids (e.g. Bayer Bug Free) can be used. Several thorough applications will be needed with organic products to control the nymphs as they hatch.
Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Plants in flower should not be sprayed due to the danger to pollinating insects.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)