What To Do If You See Citronella Ants In Your Landscaping

Late into the summer, it's not uncommon to come across a trail of meandering yellow crawlers, otherwise known as citronella ants (Lasius interjectus), in your landscaping. Fond of moist and secluded areas, these subterranean ants are quick to nestle underneath logs, in potted plants or yard vegetation, on decaying wood, and under patios. Some even build colonies in the soil surrounding a home's foundation, eventually entering the structure through crevices or heating ducts. Unconventional soil warming (via heating vents, for example) can sometimes stimulate late-season swarms.

As these large yellow ants aren't particularly damaging to the landscaping or your home's structural integrity, many recommend leaving them be, as they will disperse after their swarming season, which barely lasts three to four days. However, since many homeowners find them a nuisance and would rather eliminate the risk of these insects establishing themselves in their yards, locating and exterminating their nest is the only choice. While applying insecticides helps control large ant infestations, it's best to seek professional help.

Identifying the citronella ant

The first step to controlling a citronella ant population in your landscaping is to verify if it's indeed the yellow ant or the closely resembling termite that shares its proclivity of building soil mounds when migrating. The biggest giveaway is the citronella ant's tendency to emit a lemony scent as a defense response when they feel threatened or are crushed. Moreover, unlike termites that eat into your wood, causing colossal structural damage, these pesky invaders aren't known for foraging, instead sticking to honeydew extracted from aphids and mealybugs.

Further, citronella ants are subdivided into various classes, such as workers and queens, that reach a length of 3/16 and 5⁄16 inches, respectively. They support a 12-segmented antenna with sparse hair covering their abdomen, head, and thorax. However, it's the ant's smoke-winged swarmer class that's responsible for infesting your yard and garden landscaping. Like workers, swarmers aren't solidly yellow and may appear light yellow or reddish-brown but are twice the worker-class size. Citronella ants don't have a stinger, significantly lowering their threat level.

Controlling a citronella ant infestation

As yellow ants don't pose an immense risk, it's typically advised to ignore their groupings unless they find a way into your home. If found inside, vacuum away the swarm, as these ants are unlikely to bite the typical ant baits — given their love for honeydew. Further, seal away all openings and foundation cracks to restrict their entry.

But if the swarms continue to recur, locate the citronella ant colony — they're generally marked by mounds of excavated soil — and inject it with insecticides. You can also use an aerosol insecticide like pyrethrin over your landscape. However, you'll need professional help to treat the citronella infestation underneath concrete, as you must first drill the slabs to detect their exact location.

Going forward, control the growth of weeds, especially dandelion plants, to keep aphids away from your lawn. This will restrict the symbiotic relationship between aphids and citronella ants, discouraging the ants' establishment. Also, spray trees with a 1% to 2% detergent solution to help rid your home's landscaping of these subterranean insects. Pruning vegetation and removing yard debris, like lumber and dead branches, should further limit the ants' nesting options.