How can I get rid of ants in a mandarin plant in a big old vat surrounded by roses?
ants are not insects harmful to plants, or at least, they are not in the vast majority of cases; they generally feed on all the remains they find, including dead insects, seeds fallen to the ground, fruits picked from the ground, aphid honeydew. The presence of ants on the leaves of plants is due precisely to this last element: ants live very often in symbiosis with aphids; this is because the aphids, sucking the sap from the foliage, metabolize only the protein component, expelling the sugary part from the abdomen, which they are unable to digest; this substance is called honeydew, and many insects are greedy, including first of all the ants, but also the bees (if you go to the supermarket, you will surely find jars of honeydew honey, well it is not produced with sugar taken from flowers, but with the sugars expelled from the aphids, and if the bees can make tons of honey, it means that there is usually a lot of honeydew on the plants). Scientific research has even shown that ants carry out a kind of aphid breeding, defending them from predators, keeping them "milked" from the excess honeydew, and sometimes even moving them on plants close to the infested one, to widen the breeding. So when you happen to have a plant with some dirty leaves of a sugary substance, the new buds are slightly damaged, and with an aspect that is not completely healthy, if we see ants on the plant, they are not doing anything to the plant itself, but are taking advantage of it of the aphids that live on it. There are many products against ants, the most used are pyretroid-based powders, which kill ants by contact: later the colony moves to another area. But the real method to remove the ants is to eradicate the aphids; these insects tend to develop starting from spring, when the climate is hot and humid and the plants are full of sprouts; there are many products against aphids, both suitable for use in organic farming and traditional products; in general, whatever type of product it is, you will need to do at least a couple of treatments, when you see the first aphids in spring, and then repeat at least a second, after 15 days; when we use a plant protection product, we always prefer the evening hours to spread it in the environment, and we avoid treating flowering plants. If your plants are in pots, it can also happen that the ants have built their anthill in one of your pots; it will therefore be necessary to repot the plants, replacing all the soil, and completely removing the anthill, which you can deposit in a corner of the garden away from the house, or in uncultivated land.