These small insects are also called plant lice; there are various species, which generally differ in color. Some species prefer certain plants in particular, such as the golden aphid of the oleander. Aphids parasitize most of ornamental plants, as well as horticultural and fruit plants; they nest on the most tender buds and around the floral buds; their mouth is specialized to break the external wall of the most tender stems and to suck the sap of the plant. The result is often a general weakening of the whole plant, the curling of the leaves, the stunted development of flowers and fruits. Often a large sticky substance, called honeydew, runs from large colonies of aphids, consisting of sugars present in the sap of plants; this substance is sometimes colonized by dark mushrooms, called fumaggini.
Often then near the colonies of aphids there are colonies of ants, which collect honeydew from the abdomen of the aphids, to use it as nourishment; the ants move the young aphids from one plant to another, to enlarge their colonies, as if they were raising them.
Aphids develop particularly when the climate is humid and cool, therefore especially during spring, and also spent during autumn; in houseplants they can develop all year round. Each new population has a very rapid development, it is therefore essential to intervene when you notice the first specimens, checking the young shoots.
Fight the aphid
Traditionally, the fight against aphids is practiced by using pyrethroids or nicotinoids, insecticides with a broad spectrum of action, harmful both for aphids and for useful insects. Pyrethrum-based insecticides are also widely used, also in this case it is a broad-spectrum insecticide, if however we try to use pyrethrum in the evening, and when the plants are not yet in bloom, we will at least avoid damaging the bees and other pollinating insects.
Our grandmothers used nicotine macerate against aphids, prepared by letting the tobacco of a couple of cigarettes soak in water for a few days; this product was considered not very harmful, as it was natural and not synthetic; in reality even the tobacco macerate is a very powerful and broad-spectrum insecticide, which damages all the insects present in the vegetable garden and in the garden.