I have a bonsai on the branches we have formed some brown shell-like parasites and by removing them underneath they are empty and they have a white powder I would like to know how they can be eliminated thanks.
the insects you found on your bonsai are cochineals, in particular cochineal with half a grain of pepper or scudetto; the hard caps that you see contain various seeds, which will give rise to a large number of insects, which will disperse on your bonsai, and in particular on the underside of the leaves and on the joints of the branches. These insects are very harmful because they suck the sap from the plants. They tend to develop especially in conditions of very dry air and poor ventilation; even if the soil is very dry, they also tend to develop around the roots. In fact they are usually among the most feared insects by collectors of succulents, but they also develop in greenhouses, or in places where plants are left indoors, with poor ventilation and little environmental humidity. To eradicate them it is necessary to use a product that is able to pierce the badges, so as to eradicate the insects that are protected by these structures. Typically, mineral oil-based products are used, because the waxy component of the shields is dissolved by the oil and thus allows the insecticide to penetrate up to the insects. On the market you will find many products against cochineal, both spray and tablets, to be inserted into the soil. In addition to using a special anti-cochineal product, I also invite you to improve the cultivation conditions of your bonsai, so as to avoid any reappearance of the parasite. If you keep the plant at home, move it outdoors, on the terrace or in the garden, in a well-ventilated area and where it can enjoy the common environmental humidity. Place the bonsai in shade or shade, to prevent the spring sun from burning its leaves. Also remember to regularly water the plant and provide a good fertilizer for bonsai, from March to September; a healthy plant, well cultivated and kept at the right exposure and with the correct environmental humidity, as well as being less likely to be attacked by parasites, also tends to avoid being damaged by any insects that may still attack it.