I have a bonsai on the branches some brown shell-like parasites have formed and removing them underneath are empty and have a white powder I would like to know how they can be eliminated thanks.

Dear Angelo,

the insects you have found on your bonsai are cochineals, in particular cochineals with half a peppercorn or scudetto; the hard caps you see contain various seeds, which will give rise to a large number of insects, which will scatter on your bonsai, and in particular on the underside of the leaves and at the joints of the branches. These insects are very harmful because they suck the sap from plants. They tend to develop mainly in conditions of very dry air and poor ventilation; even if the soil is very dry, they tend to develop around the roots as well. In fact, they are usually among the most feared insects by succulent plant collectors, but they also grow in greenhouses, or in places where plants are left indoors, with poor ventilation and little ambient humidity. To eradicate them it is necessary to use a product that is able to perforate the badges, in order 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 to the insects. On the market you will find many products against cochineal, both spray and in the form of tablets to be inserted into the ground. In addition to using a special anti cochineal product, I then invite you to improve the cultivation conditions of your bonsai, in order to avoid any reappearance of the parasite. If you keep the plant indoors, move it outdoors, on the terrace or in the garden, in a well-ventilated area where it can enjoy the common ambient humidity. Place the bonsai in partial shade or in the shade, to prevent the spring sun from scorching the leaves. Also remember to water the plant regularly and to 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 not to suffer damage from any insects that should still attack it.