Scale insects and false shields are most often introduced with new plants and soil. The shield is a nasty pest, sometimes very dangerous - males can fly, spreading to other plants, but fortunately they have a short life cycle. Females are wingless, there are usually more, but they live longer.
The scutellum kills plants slowly but surely. The worst thing is to fight it on small-leaved plants. Hot water helps, but it's bad - shields protect. In addition, young insects, still in the larval stage, are very mobile, instantly settle throughout the plant, they are called "vagrants." They are so small and transparent that they are invisible until the plant begins to turn yellow or adults grow.
There is an opinion that when something threatens the shields (chemicals, adverse weather conditions, etc.), then more males appear, under normal conditions more females are formed. This only suggests that if you undertake to remove the shield, remove it immediately and cruelly, until the plants are completely recovered.
Shield on houseplants - how to fight
Shield on houseplants - more about the pest and control measures.
Lynx: I got rid of washing the leaves with a solution of household soap + spraying and watering with Aktara. In the ground, shields are unlikely to start, because these bugs are piercing-sucking reptiles, for reinsurance when treating a plant, it is better to cover the pot with the earth with a bag, and later change 2-3 cm of the topsoil with a new substrate.
Alex: Recently (15-20 years ago), when there were no modern pest control drugs, soap and oil emulsion was used to get rid of shields: 1 tablespoon of engine oil and 2 tablespoons of powder are diluted in 1 liter of water, shaken to get a homogeneous mass and sponge applied to the plant, thoroughly wiping all twigs and leaves on both sides. Leave for half an hour (the shields swell and suffocate during this time) and wash off under a strong stream of water. Perform 3-4 treatments at weekly intervals. I warn you, at that time washing powders were not so poisonous even without bleaching properties! It is better to use phytoverm for destruction at home - the hazard class is low for humans and animals.
Goldie: If not lazy, then rinse into the hand - with cotton wool. The shield is easily crushed. And if you can't, then wash the flower - this is if there is not a lot of it. And if there is a lot, then you will have to cut off the severely affected parts, it is easier to observe and treat. And then the plant will grow. To fight the shield seriously (if the lesion is severe), chemicals are needed, folk methods from the shield do not help. I used an actellic, sprayed on the balcony.
Odina: my citrus with a shield lived for two years until I found out about Aktara. At home cat and dogs. And it was because of them and the children that I did not use insecticides, and I watered the actara 4 times with a weekly break and an adyu shield. Then, about a month later, I noticed one adult specimen, (apparently one vagrant survived somewhere) once shed and that's it - I haven't seen these reptiles for 8 months.
Severina: The remedy "Doctor," the active substance like actara, is only in tablets. It fits against shields. The fundamental difference with the usual actara is that if you breed it and spray the plant, the poisonous effect on the pests occurs immediately, and the tablets of the drug Doctor must be applied to the ground, wait until the actara dissolves there and is absorbed by the roots of the plants. That's only then the plant will become poisonous to the pest. Additionally, you can wipe the leaves and trunk of the monster to remove emerging individuals until this drug works.