Ants can cause concern but they are a nuisance rather than destructive pests. They feed mainly on insects, including other ants. They also look for the sweet liquid known as honeydew which is excreted by aphids and some other sap-feeding insects.

Damage

Ants can protect aphids from attack by ladybirds and other predators in order to secure their supply of honeydew. Increased numbers of aphids may result in more damage to plants. However, ants do little damage to plants themselves, except by disturbing soil around plant roots and depositing it on the surface during their nest building activities. Some ants (mostly Myrmica species - commonly known as red ants) can sting, but for most people this is no more than a minor irritation.

Control

Unless their nests are particularly troublesome, ants are best left alone. If a colony is destroyed it is likely that its place will be taken by incoming queen ants, which take over the territory and establish new nests. Disperse ant heaps on lawns by brushing the excavated soil on a dry day before the lawn is mown, otherwise the soil will get smeared on the lawn surface by the mower. If the lawn has an uneven surface due to years of ant activity, peel back the turf in the raised areas, remove excess soil and relay the turf. This is easier to do in the autumn or spring when ants are less active.

Many proprietary ant powders, baits, sprays and aerosols are available for controlling ants in and near buildings, but these are not suitable for general garden use. To make a real impression on ant numbers it would be necessary to destroy the nests rather than just the foraging ants. That is difficult to achieve as ant nests occupy a much larger volume of soil than might be suggested by the small heaps of soil excavated on to the surface.