Ants and aphids: why fighting one without the other is pointless
Ants on your fruit trees are no accident — they're tending a herd.
Gardeners usually treat ants and aphids as two separate problems. In reality, they are one problem, and addressing them separately is ineffective.
Ants feed on honeydew — the sugary secretions of aphids. To maintain this food source, they behave like herders: they carry aphids onto young shoots, protect them from ladybird beetles and lacewings, and take their eggs into the nest for the winter before returning them to plants in spring. With this care, aphid numbers grow many times faster than they would otherwise.
The practical conclusion is that treating aphids without addressing the ants produces only a temporary result. The ants will restore the destroyed aphid colony by bringing in aphids from neighbouring plants, and in two or three weeks the problem will be back where it started.
An effective approach has two parts. The first is to restrict access to the plants by fitting sticky tree bands around trunks and removing dead bark where aphids overwinter. The second is to target the ant nest itself rather than the foragers. Delayed-action baits and gels work here: worker ants carry the bait into the nest and feed it to the queen and larvae. A product that kills on contact does not reach the nest and therefore only creates the appearance of success.
Patience is also required: with baits, the first visible effect appears after a few days, while complete colony collapse takes two to three weeks. Digging up the nest with a shovel is faster, but usually only causes the colony to move a few metres away.
