Ants are a common sight both in the garden and, much to our chagrin, inside the house. These much-maligned, yet misunderstood creatures may not be your favorite form of wildlife, but they have important work to do. Before the sight of them sends you screaming for that spray can of death, take a moment to consider when they are a nuisance to be managed, and when you can leave well enough alone.
The living habits and lifestyles of ants varies by species, but all are social, living in colonies numbering from thousands to millions of workers. Each colony has one or more queens, who are responsible for laying eggs, and several males whose only purpose is to mate with queens from other colonies. Called a “mating flight,” this is when you might see winged ants, which are sometimes mistaken for termites.
Worker ants are responsible for tending the young, maintaining the nest, and foraging. Their activities provide many critical services to our ecosystem:
- Decomposition: Ants feed on dead insect and animal tissue, an important way of recycling this organic matter back into the environment (yes, animals are considered “organic matter”!)
- Weed seed predation: Seeds are a source of protein for ants; “squirreling” seeds away in their nests means fewer weeds for the gardener to yank out
- Insect predation: Ants are the top predators of termites; other favorite snacks are caterpillars and fleas
- Soil aeration: The nest-building activities of ants create air channels for air and water to move through, which is great for plant roots
- Plant guardians: Certain plants and ants have a fascinating relationship wherein the plant provides delicious nectar via extrafloral nectaries (nectar located on the plant outside of the flowering structure) to attract ants, who repay the plant by fending off herbivores
As wonderful as these services are, not everything is rosy in ant-human relationships. Besides fending off herbivores, ants also place and protect aphids, scale, mealybugs, and other sucking insects on plants to collect the sweet honeydew secreted by these pests as they feed. Certain species, such as the carpenter ant, can cause structural damage to buildings, as they like to nest in wood; and let’s not forget the disgust of discovering a trail of ants roving across your kitchen counter!
As far as the outdoors is concerned, attempting to exclude ants from your property is both impossible and undesirable for the beneficial reasons listed above. If ants are bringing aphids and scale to your plants, either use bait stations around perennials, or try Tanglefoot to keep ants out of trees. Aphids can be sprayed off plants with water; avoid using pesticides, which often kill their natural enemies (e.g. ladybugs, solider beetles).
Ants usually only enter buildings to escape extreme heat or cold, when searching for water in dry weather, or if they smell food laying about. If you see ants in your house, spraying should be your last resort; this short-term solution fails to address the underlying causes. The following steps are less toxic and more effective in the long term:
- Follow the ant trail and find what they are attracted to
- Clean up any spilled food (including pet food), and water; place stored food in sealed containers, and take out the garbage
- Wipe up ant trails with soapy water to wash away their scent to prevent more ants from following in the footsteps of previous foragers
- Locate and seal cracks that serve as ant entrances
- Try to ID the ant species using the tool found on the UC Integrated Pest Management website: www.ipm.ucdavis.edu/TOOLS/ANTKEY/
- Select the appropriate bait and management strategy listed on the webpage for each of the common household ants: www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7411.html#LIFE
Bait stations are preferred over sprays because ants can take the poisoned food back to their nest, killing other ants in the colony. You can purchase bait stations or make your own (see the website above for more information). Do not use a stronger concentration than suggested, thinking that “if a little is good, a lot must be better”, or the ants will die before reaching their colonies, making the bait station less effective.
One species of ant deserves special attention because of their painful bites and stings. The imported red fire ant (Solenopsis invicta), hailing from South America, is infamous for its aggressive attacks when defending their nest. The California Department of Food and Agriculture has a red fire ant eradication program; if you discover them on your property, call the CDFA fire ant hotline at 1.888.434.7326 before attempting to deal with them yourself.
Most ants you find in the garden are not looking to invade your home unless you give them the opportunity. Taking simple steps in proper food storage and sealing up your home goes a long way toward keeping them out in the garden where they can be of most benefit to everyone.