There is discussion as to whether or not ants are harmful to gardens. Some people claim they are beneficial, while others suggest an immediate treatment plan. The truth is that the severity of ants in the garden depends on the species and activities of the ants. Many ants provide benefits such as pollination and killing off plant-eating insects, including caterpillars. However, some species of ants promote the growth of aphids, which destroy plants. Fire ants are harmful, and should be treated if present.
When trying to determine the severity of an ant infestation in the garden, begin by checking aphid population levels. Aphids are very destructive to gardens. Aphids secrete a sugary solution that is eaten by ants. Because of this, ants begin to ‘farm’ aphids. Ants protect aphids from predatory insects, and have even been known to carry aphids around. If it appears that ants are contributing to growing aphid populations, then the ant colony is a problem. Fire ants are a growing problem in the Southern US. These ants deliver a stinging bite to humans, and thousands of them can infest a garden.
Baiting ants is an effective form of control. Boric acid mixed with sugar, peanut butter, or jelly will attract ants to the bait. Smaller concentrations of boric acid allow ants to carry the poison back to their colony before dying. Insecticide sprays are also available that can destroy ant colonies. Be sure to check the label of insecticides to verify that they are safe to use near edible garden plants. Fire ants or difficult to eradicate, and are best controlled by professionals.