I have tried to kill them with Neudorff Spruzit spray (Pyrethrin) and Provanto spray (Flupyradifurone) and they still keep spreading after 2-3 months from first poisoning. I really need help because now they spread somehow in my Thai constellation monster.
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It is hard to see the insects in the pictures and the damage done to the plant looks extensive.
If these are scale, spraying with an insecticide is next to useless. Insects like adult scale cover themselves with a hard shell that protects them from most insecticides. The juvenile stage, which are called 'crawlers' are the only ones exposed to a sprayed insecticide.
Unfortunately, you are going to have to remove them by hand with Q-tips or cotton facial pads dipped in rubbing alcohol. After you have removed all the ones you can see with the cotton swabs/pads then you need to spray the entire plant with a modified soap spray. The one I like to use is mix a few drops of Dawn dish liquid, about 3-4 tablespoons of rubbing alcohol with distilled water in a spray bottle. Spray the plant thoroughly, making sure to get all stems and leaves. You will need to repeat the process every 3 days until there is no longer any sign of the insects. This process will also get rid of any other type of insects, if we are mistaken about the identity of the insects
It looks like you have a very high insect infestation on your plant so you will have to be diligent to remove them. Don't forget to check all other plants you have in the same area as this one. It is likely the infestation would have spread to other plants nearby. If they are infested too, they will need the same treatment
A systemic poison should get them . Regular sprays do not reach them under the shell . You can't use systemic on a food or spice plant. I need hours to scrape larger scales off my sweet bay bush because I don't use systemic on it.
