On this early July morning, Kim was getting her morning coffee and, sure as June Gloom goes away by July 1, so the Argentine red ants that have marched their way up from Patagonia have returned for another summer of fun, watching Kim pull out the stops with all her anti-ant programs. Kim will not kill a spider, but she gives no quarter to ants. They are her mortal enemy because ants impugn her good housekeeping even though their presence has less to do with poor cleaning habits and more to do with their never-ending search for water.
Argentine ants (Linepithema humile) are one of the most successful invasive species in the world, and Southern California hillside properties like ours are prime territory for them. They show up in summer because they are chasing moisture. As hillsides dry out in summer heat, ants move toward irrigated landscaping, gardens, and homes in search of water, which is why we get a wave of them just as things heat up. They have obviously spread the word to all their brethren than this particular hilltop has a 25-zone irrigation system and a more than normally verdant gardener at its helm who likes to keep things green all summer long. Our friend Melisa like to say that its always dry on the chaparral except for this one spot where it rains every day…and that spot would me my well-watered hilltop. We are a favored home to bunnies, quail and rattlesnakes, but also to Argentine red ants. A second wave of our little red friends from the South also often comes after the first fall rains for the same reason.
What makes these little Red Devils different from native ants is that they are very small (about 1/8 inch), light-to-medium brown, sometimes appearing reddish and give no painful sting like native harvester or fire ants…which makes them friendlier and actually less troublesome…except in their numbers. They form massive interconnected supercolonies rather than single-queen colonies. Colonies from San Diego to northern California are genetically similar enough that ants from different nests don’t fight each other, which is a big reason they’ve displaced native ant species so thoroughly. Seems like there might be a lesson in that fact for mankind in these days of increasing nationalistic antagonism. These colonies have multiple queens per colony, so killing a few doesn’t do much to the spread of these little buggers.
There are many reasons why these little guys are so hard to beat. Spraying visible trails usually just splits the colony and makes it worse, with surviving ants “budding” off and forming new satellite nests. Slow-acting bait (borax/sugar-based) that workers carry back to the queens is far more effective than contact sprays, but knowing where to put that is very challenging. The professional solution for managing them on a hillside property like ours (we actually have 2 exterminator companies on retainer) suggests that we trim vegetation and irrigation lines away from the foundation of the house since they follow moisture along drip lines and plant roots. We should put outdoor bait stations along their trails since supposedly that works better than indoor spraying. The exterminators spray outdoors around the foundation, but I always wonder if that does much.
Our original cleaning woman, Isabel, was brilliant at controlling Argentine red ants, which we experienced in an out-of-control swarm in the very dry summer of 2020. Between COVID and Argentine red ants it started to feel like the end of the world up here. Isabel had this secret and supposedly unsanctioned (by the FDA) “Chinese Chalk” that seemed to work magic. “Chinese chalk” usually refers to insecticide chalk sticks, often sold under names like “Miraculous Insecticide Chalk” or “Chinese Chalk”, that you draw a line with around the house or even counters to repel or kill crawling insects like ants and roaches. Most versions of this pernicious stuff contain deltamethrin or cypermethrin, which are synthetic pyrethroids that are legitimate, EPA-registered, active ingredients when formulated and labeled properly. The problem isn’t the chemical class; it’s the product. These products are typically manufactured in China or Southeast Asia without EPA registration, meaning there’s no oversight on concentration, purity, or contaminants. Labeling is often absent, wrong, or only in Chinese, so you don’t actually know the dose you’re applying. They’re technically not legal to sell in the US, so you’ll mostly find them at flea markets, some ethnic grocery stores, or online marketplaces like Amazon/eBay (where they get pulled periodically)…they are sort of the back-alley, car-trunk items of the suburban black market around here. Pyrethroids are toxic to cats especially, and to fish/aquatic life if it washes into runoff. We don’t have cats and these are no fish ponds up here but I suppose I should wonder about my basalt fountain, since the local birds and hummingbirds do love to bath and take a drink at it.
There is still a need for a practical alternative for Argentine red ants specifically, since as the detractors of chalk would point out, it isn’t a very effective tool since it kills ants on contact but doesn’t reach the queens, so the colony just re-routes around the treated line…which seems somewhat borne out in practice. The research suggests that a boric acid or borax-based bait (like Terro) that little red ant workers carry back to the nest will actually knock down the colony rather than just redirecting foot traffic on the patio. I am also told that I should suggest to Kim that a pyrethroid-based product, like the EPA-registered versions (Ortho Home Defense, Spectracide, etc.) contain the same class of chemical as the Chinese Chalk and yet has known concentrations and proper safety data, and therefore may represent a better choice than an unlabeled import, especially around a property with a fountain. That all said and done…there is something that feels more effective in buying secret formula stuff in a back alley, right?
So far Kim has only seen a few ants and they have been around the in-wall coffee maker, which is just fine by me since I never touch coffee in any form. Perhaps the in-wall water lines aren’t properly shielded from the foundation and the ants follow those lines into the kitchen…who knows. I can always tell when it gets bad based on the amount of swearing and cursing I hear from Kim in the morning from the kitchen. So far, all I’ve heard is the opening war cry of, “They’re back!”