Aphids

Aphids are also called plant lice and are pear-shaped insects that suck nutrients from plant leaves. We have many types of aphids including green peach aphid, black bean aphid and green apple leaf aphid.
Leaf aphids mainly damage young plants by sucking up sap and emitting  a poison that causes leaves to curl. They also produce a sugary substance called honeydew. The sugar secretion is used as food by ants (and flies) and if the ants do not feed on the sugar secretion, it spreads on the plants  and is therefore colonized by the fumaggine which prevents the correct activity of chlorophyll photosynthesis.

Aphids spend the winter in the form of eggs and preventive treatment should be done during this period when they are in the embryonic stage.  

Natural enemies of aphids par excellence are ladybugs, then there are predatory bugs, sirphs, and chrysopes. Ladybugs can now be found live online and can be included as a biological fight. If they are few and are taken in time, it is also possible to intervene on single plants manually by crushing them, but usually when one notices it they have already colonized various parts of the plant.

Natural remedies: the nettle macerate, the garlic infusion, the tomato leaves and feminelle macerate, the fern macerate, the horsetail decoction and the horsetail macerate, marzilia soap are remedies that are easy to self-produce.
Mechanical remedies: use a strong jet of water on the plants 
Chemical remedies: treatment of preventive white oil for the first phase and then treatments with pireto or systemic insecticides.