Ants

Various Formica, Lasius and Myrmica species

Ants rarely do any direct damage to plants, but their mining can kill roots, and their effects are secondary. But their anthills are a nuisance in lawns and borders.

Symptoms

Ants crawling over structures and plants – either individually or in large numbers
Anthills – mainly in lawns
Plants, including those in containers, may start to wilt
Swarms of flying ants in summer

What are ants?

Ants are small insects whose bodies are recognisably divided into three sections – head, thorax, abdomen. They are closely related to wasps and bees.

While some live in small colonies, most species are social and live in large colonies of many thousand or million individual ants all working together to support the colony. Colonies mainly consist of sterile, wingless females – the workers, soldiers or other specialised groups – plus some fertile males, called drones, and one or more fertile females called queens. The queens lay eggs in brood chambers within the nest, which develop into white, maggot-like larvae. The wingless females gather food for the colony, feed and tend to the larvae and maintain and guard the nest.

At certain times of year, mainly during humid weather in summer, the nests produce winged ants. These are young queens and fertile males. They usually emerge from the nests in large numbers – often swarms – fly up and mate. After mating, the males die and the queens go off to find suitable places to establish new nests.

What do they affect?

Widespread throughout the garden and on numerous plants
Lawns
Container plants

Ants do cause concern to some people, especially as some species (especially red ants) can bite or sting. For most people, apart from those who are allergic, this is a short-lived, minor irritation.

In the garden, they are mostly a nuisance rather than a destructive pest.

They do little direct damage to plants, although their mining in the soil can damage or kill roots that can cause plants, especially small ones, to wilt. They sometimes produce nests in containers where, because of the restricted root growth, this can be more damaging.

Anthills produced in lawns can be a real nuisance, spoiling the appearance of the lawn and making it impossible to mow correctly.

Ants mainly feed on other insects, including other ants, which means they can be useful in clearing away and tidying up dead insects, and controlling insect pests.

However, they also collect the sugar-rich honeydew excreted by aphids and other sap-feeding insects, such as scale insects. So, when they are seen on plants, they are mainly collecting this honeydew. They even “farm” aphids, moving them to the tips of shoots and other young plant growth where most of the sugars are inside the plant. They will also fight off ladybirds and other aphid predators to protect the aphids from attack, to ensure this supply of honeydew.

How to control ants

Controlling individual ants is time consuming and not worthwhile. Where they are troublesome, you need to find and destroy the nest.

Unless a nest is a particularly nuisance – such as in the lawn – they are best left alone. If a colony is destroyed, an in-coming queen will probably take over the area and establish a new nest.

Non-chemical control

Nests and anthills can be destroyed by watering on the biological control based on nematodes.

Chemical control

There are numerous sprays, powders and baits available to control ants. But you have to find and treat the nest, rather than trying to kill individual ants.

Prevention

You can’t prevent ants from coming into your garden and building their nests – wherever they want to build them.