A negative association for some garden plants.
All gardeners growing roses had a day or another to fight against the ravages of plant lices. Very often among the aphids, we can see the presence of ants. It is not a coincidence that the ants and aphids are often seen together. Indeed, the two species of insects have developed an extraordinary symbiosis that benefits to the both of them. Aphids suck the sweet sap of plants for food. They excrete the sugars that they can not assimilate. This liquid is called honeydew . When an ant stimulates an aphid with its antennae the insect produces honeydew . The flow of sweet liquid is guided by the cauda on the end of the abdomen. The ants protect and raise aphids as livestock. They protect their herd from ladybugs and other predators attacks. In addition, ants favor larger aphids who produce more honeydew. In doing so, they perform a genetic selection beneficial to both species. This symbiotic relationship involving the exchange of honeydew for protection is called trophobiosis.
In large number, the aphids can cause the deformation of the leaves and affect the plants growth. By pricking the plant tissues to feed, the trophobionts can transmit diseases to the host plant.
For preventive protection, you can plant Marigold, thyme or mint among the sensitive plants to aphids. These plants keep these little pests away from the garden.
If the infestation is difficult to control, you can use an insecticide containing natural pyrethrin. Otherwise, you will not have the choice to use a systemic chemical insecticide.