Ants
Formicidae
Ants eat almost nothing you grow. What they do is farm the aphids that do — and undermine roots with their nests, which is the real damage.
How to know it
Everyone knows an ant. What matters in the garden is the behavior: a steady two-way column running up a stem to a colony of aphids, ants stroking them for honeydew and driving off the ladybird larvae. On the ground, a fine crater of excavated soil around a nest entrance, often between paving slabs or under a pot.
What you'll see
- A column of ants running up and down a stem to an aphid, scale or mealybug colony.
- Aphid numbers rising on a plant the ladybirds have plainly visited but not cleared.
- Fine excavated soil heaped around a nest entrance, in a lawn, a path, or under a pot.
- A plant wilting in dry weather because a nest has hollowed the soil out around its roots.
- Sticky honeydew and sooty mold below the farmed colony.
Where it comes from
A colony of a queen and her workers, persistent in one place for years, tunnelling and moving soil constantly. Many species farm sap-sucking insects deliberately — moving them to fresh growth, defending them from predators, and in some cases overwintering their eggs. Winged queens and males fly on a warm, humid day in midsummer and start new colonies.
Warm, dry, well-drained soil, and gardens with plenty of aphids. Nests concentrate under paving, in dry banks, in pots and along wall bases. Numbers rise sharply in a dry summer.
Dealing with it
- Deal with the aphids and the ants lose interest; the aphid is the reason they are there.
- Band the trunk of an affected tree or shrub with a grease band or sticky barrier so the ants cannot climb to the colony.
- Water a pot or a plant with a nest under it thoroughly and repeatedly; the colony will usually move rather than drown.
- Brush the excavated soil back into the lawn on a dry day and level as you go.
- Do not scatter ant powder through a border. It kills ground beetles and the ants come back.
Keeping it out
- Keep aphid numbers down and the ant problem largely disappears.
- Water plants steadily; a well-watered soil is less attractive for nesting and a plant with a nest under it copes better.
- Fill and point gaps in paving where nests establish.
- Grease-band fruit trees in spring.
- Accept ants in the wider garden. They aerate soil, disperse seed, and take a great many pest insects themselves.
What it goes for
Nothing is eaten directly. Roses, apples, cherries, broad beans, peonies and pot plants suffer from the aphids they farm and the nests they dig.
Trouble it brings with it
See also
The Cottage Garden Companion — the gardener's bestiary at cottagegardencompanion.com