Description
In New Zealand, there are 39 species of ant. There are 11 native species, and the remainder are introduced. Most species in New Zealand are less than 3 millimetres long. The largest native species is about 6 millimetres long.
Ants live in colonies and behave as social insects. Usually, the colony is made up of one or more queens and many workers. The queens remain in the nest and lay eggs and workers take care of them. To effectively control ants, you need to kill the queens as they produce the eggs for the colony.
Ants prefer building their nests in warm, dry locations. Nests are usually found in the ground or inside buildings, decomposing logs, and underneath plant pots and pavers.
Worker ants are sent from the nest to search for and collect food. When food is located, they return to the nest and lay a pheromone scent trail to the food source. This allows other worker ants to follow the trail to the food source. Food is then gathered and returned to the nest and fed to the colony. This is why baiting programmes are effective in controlling ant nests.
Ants can be easily spread by human activity. In a nursery they can be spread in potting media, freight, vehicles, containerised plants, and production materials.
Symptoms and damage
Ants commonly form symbiotic relationships with sap-sucking insects such as aphids, scales, psyllids, mealybugs, whiteflies and leafhoppers. Ants “farm” these pests by protecting them from predators in exchange for the honeydew they secrete. They also feed on their eggs. Ants are known to move these pest insects from plant to plant, further spreading infestations. Honeydew produced by sap-sucking insects can have a negative effect on plants by inhibiting photosynthesis, which can affect plant growth. It also provides a breeding ground for fungi including sooty mould.
Ants are known to carry away freshly planted seed to their nest.
Ant infestations can cause problems in homes and buildings. They can invade cupboards, sealed containers, electrical areas, wall cavities, clothing and bedding, and can contaminate food.
Prevention and control tips
- Baiting programmes are effective in controlling ant nests. Place bait near ant trails and regularly monitor and refresh bait. Application may be required for 4 to 6 weeks to ensure that new ants that hatch from eggs during that time can be treated.
- Investigate if ants are acting as predators or “farmers” of insect pests before deciding to use control measures.
- Control sap-sucking insects, for example, aphids and scales to eliminate the ants’ food source.