Ants are not a significant garden pest, unless of course you want an enjoyable family picnic in the lawn. These tiny creatures have an amazing societal system which is typically what causes their irritating garden behaviors.
For most species, control is only necessary in the garden if the population gets out of hand. Garden varieties do not actually eat plants or actively destroy any plant matter. Their main source of food is sugar, usually found in nectar, sap, or the honeydew excrement from aphids. In some cases, garden ants can actually be a beneficial insect as they will kill off more destructive pests like caterpillars. They are also natural soil aerators through their extensive tunneling systems. As food for beneficial animals such as birds, lizards, and toads, they will also encourage wildlife to flourish in your garden.
Although the mild-mannered outnumber the problem populations in most areas, there are two species to watch out for.
Carpenter ants are a quick disaster to any wooden structure. Major forces that can tunnel, nest, and destroy old wood in a relatively short period of time; these insects are a known hazard to your home. Even in the garden they can be treacherous, attacking backyard play structures, trellis, and garden sheds.
Anyone who has had a personal run in with a fire ant colony can easily consent to the significance of their hazard to humans and animals. There is a reason they carry the name "fire," as the sting from these insects creates severe pain and even allergic reactions in some people. Of the ant species, these are the most destructive and dangerous in the garden. Not only can their battling stings hurt, the poisons are capable of killing small animals, reptiles, and birds. Their extensive social nesting system can cause major damage to garden plants. As the worst offender of the ant family, if they are present in your garden, it is time for some control methods.
No matter what types you want to reduce, the control methods are similar. As any species can hurt plants by mining nests around roots, if they are excessive in your garden, you will want to reduce the population. They are most problematic to new plants with young roots and lawns. In lawns, you know they are present when you see nest mounds that smother the grass and create unsightly patches. An easy solution to this problem is to grow your grass longer to hide the patches and live with the ants. If this is not your preference, you will have to treat the nests.
In addition to their nesting structures, they have another characteristic that can quickly create a problem in your garden - farming other insects. Certain varieties actually farm aphids for their honeydew. This can quickly create a rather significant aphid problem in your yard as the ants will kill off their natural predators.
When controlling colonies, you cannot simply kill off the individuals. You must either redirect their efforts or completely eradicate the nest. As ants are generally a non-invasive pest, it is always best to use non-invasive controls.
Treating the Nest
Insecticides that kill ants are Diazinon or Carbaryl, both are biodegradable after a few days. Organic gardeners prefer the chemical pyrethrum for control. Although it is safer environmentally, it does kill off other beneficial insects.
In many cases you can control their efforts and not have to completely eliminate them. If you have a variety that likes to tend the sap sucking insects on trees, you can keep them out of the tree through redirection. Basically, you block their path with sticky barriers around the trunk, pruning low branches, and natural barrier products such as diatomaceous earth or cinnamon powder sprinkled around the tree.
Generally speaking, you can easily retrain your ants to avoid the areas of the yard you don't want them in and send them off to the parts where they can actually be beneficial. Two easy kitchen methods are honey and apple cider vinegar. Honey will lure them and apple cider vinegar discourages them. Place a small jar of honey where you want them to live and spray apple cider vinegar on their paths that lead to the places you don't want them to go.