The Great Foragers: A Pacific Northwest Homeowner’s Guide to Odorous House Ants

Ants crawling on a piece of bread searching for food

This blog post was written by Caleb Goertz, service technician at Interstate Pest Management.

Picture this scenario: it is early April and the long, gloomy Pacific Northwest winter is finally ending. You spring out of bed feeling energized by the warmth and sunlight and head to the kitchen to make your morning coffee, only to find that someone has been up before you and has likely been going through your cabinets all night. Maybe it is just one or two on the countertop, or maybe there is a full-blown trail going to and from your dog’s food bowl. 

Either way, you’ve got ants, and most likely you’ve got odorous house ants (Tapinoma sessile). You can probably relate to this experience, as the odorous house ant (OHA) is arguably the most common insect pest species found in the home or office across the Pacific Northwest and one of the most common in all of North America. 

What Do Odorous House Ants Look (and Smell) Like?

OHAs measure between 1/16th and 1/8th of an inch in length—good luck making that measurement—and brown or black in color. Many online sources will tell you that if you crush them you will detect an odor of rotten coconut, an odor that many may find difficult to identify, considering… who knows what a rotten coconut smells like? Regardless, they do emit a slight odor when crushed which is a defense to make them less palatable to predators. 

Odorous House Ants vs Carpenter Ants

A common concern that many of our customers have is that odorous house ants are carpenter ants, a species known for their ability to do significant damage to the wood of a structure. Unlike carpenter ants, OHAs do not do any structural damage to the home. A quick way to distinguish the two common ant species is that OHAs are monomorphic, meaning they are all roughly the same size, while carpenter ants are polymorphic, meaning that individuals vary in size. If you can see multiple individual ants around you should be able to tell pretty quickly if the ants are about the same size. If you need help with odorous house ant identification, reach out to Interstate Pest Management for help.

Are Odorous House Ants Dangerous? 

Besides ruining your morning when you realize you forgot to cover those cookies last night, what do OHAs actually do? Luckily, they rarely bite, and when they do, it doesn’t hurt. OHAs are considered a nuisance pest because they don’t pose a significant health risk, nor do they cause structural damage to your home. However, they invade indoor spaces in search of food and water quickly, and did we mention… the smell?  

Why Do I Have Odorous House Ants in My House? 

In a previous blog post, we shared why ants love your home, in general. When it comes to OHAs, they are persistent foragers dedicating hundreds or even thousands of workers to the task of finding food and water for the colony. While it may seem like they are particularly picking on you, they are common indoors and outdoors in urban, suburban, and rural environments, and they assist with the breakdown of organic matter and nutrient cycling. The fact that they can persist in so many types of environments, including ours, is a testament to how incredibly adaptive this species is. 

But like with any pest species, just because they provide an important ecological function does not mean that you have to let them run rampant in your pantry. Using Integrated Pest Management (IPM) principles, Interstate Pest Management can provide you with treatments that minimize or even eliminate ant activity in the home, while minimizing harm to the environment or non-target species. 

Tips for Odorous House Ant Prevention

When OHAs show up in the home, the first question we should ask is what are they after? The answer should not surprise you. They are primarily after food and water. Part of what makes them so successful in a wide range of settings is that they are “generalists” meaning that they can utilize a wide range of food sources. However, they have been shown to prefer sugary foods as they likely evolved to subsist largely on aphid honeydew and nectar from flowers.

Tip #1: Minimize Food and Water Availability 

To prevent ants at home, limit food and water access. Regularly clean surfaces, seal food, store pet food overnight, and fix leaks to deter OHAs. 

Tip #2: Trim Vegetation 

To prevent pests from entering your home, trim or remove vegetation touching the exterior. This reduces entry points and ensures exterior pest control treatments remain effective. Also, eliminate any other potential bridges that pests could use to bypass the protective barrier including leaning shovels, boards, etc.

Tip #3: Seal Visible Holes   

While it’s suggested to patch up holes around the house to prevent OHAs,  it’s unrealistic to locate and close off every potential entry point of a house, due to their size. Instead, focus on reducing potential entry points as a way to minimize OHA issues. 

So, you’ve kept the kitchen clean, you closed the food, you trimmed back the grass, you patched the holes, but you’ve still got OHAs. More likely, you’ve kept up with the above suggestions as much as you have been able while also balancing the ten thousand other things on your plate. That’s where a professional pest control company comes in. 

The Best Way to Get Rid of Odorous House Ants

The best proactive way to get rid of OHAs in the house is by enrolling in a year-round quarterly pest control plan. Interstate Pest Management’s All Season Pest Service plan gives you access to decades of ant control and extermination experience. Each quarter, a licensed pest control technician administers a liquid residual treatment to the exterior of the house, serving as the first line of defense against general pests, including OHAs. For many of our customers that will be all that needs to be done, but sometimes an issue pops up inside. 

Do One or Two Odorous House Ants Inside Mean I Have an Infestation? 

The one or two OHAs that you see crawling around the countertop are known as “scouts” and they are looking for a food or water source, and when they find something they lay down a pheromone trail for other ants in the colony to follow. This does not mean you have an infestation. Seeing scouts is a sign that there is a colony close enough to explore the resources in and around the house, but does not mean that they have found anything useful yet.  

Why DIY Ant Control Doesn’t Work

To explain why do-it-yourself (DIY) ant control methods often fail, it’s important to first address common misconceptions about treating OHAs and then get the facts about odorous house ants and their behavior. 

Misconception #1: Constantly Spraying for Ants Solves Your Ant Problem

“Can’t you just find the colony and destroy it?” One of the misconceptions about treating OHAs is that technicians will spray an insect-repellent barrier that will deter ants from entering the house. While many of these products do exist, and some can be bought over the counter, treating OHAs with a repellent is largely ineffective and can even exacerbate the issue. 

Misconception #2: Squishing Ants Solves Your Ant Problem

This misconception involves the belief that squishing ants individually reduces their numbers effectively over time. However, this tactic doesn’t actually work as anticipated. 

Understanding Odorous House Ant Behavior 

Ant colonies typically consist of a queen who gives birth to all of the individuals within the colony. In the case of OHA colonies, multiple nests and queens are common. Queens exhibit a remarkable ability to monitor their workforce, keeping track of the number of workers foraging in the field and adjusting population levels accordingly. With the capacity to lay dozens of eggs in a day, a queen can easily replenish lost workers if, for instance, 300 workers venture out and only 250 return.

Of greater significance to OHA treatment is the phenomenon of colony “budding.” This occurs when a queen and a group of workers set out to found a new colony, often triggered by environmental stressors. Factors such as repellent use or the application of products that kill worker ants on contact can induce stress, prompting a queen to seek out a better area to find resources and avoid the stressor. Thus, what was once a single colony can split into two. This is a key reason why many people find that despite their efforts to spray and eliminate ants, the problem persists and may even worsen over time. 

How Pest Control Companies Treat Odorous House Ants 

Interstate Pest Management uses modern ant treatment tools that eliminate the need to find the nest or individually kill every ant to eradicate the colony. Instead, we let the worker ants do it for us. Our exterior and interior treatments are “invisible” to OHAs, ensuring they unknowingly spread the product throughout the colony. Studies have shown that even a single ant coming into contact with the product can eliminate a colony of hundreds. 

Baiting is also commonly used indoors, where these products function similarly. However, ants are aware of the bait, thinking it’s a food source, and carry it back to feed the queen and larvae. While many over-the-counter ant baits are available, some are too strong for OHAs. This means that the individual ant may pick up the bait but die before reaching the nest. Our technicians are experts at evaluating when and where products can be applied safely and effectively.

Odorous House Ant Treatment Near You

As we eagerly await warmer weather, so do OHAs. Plan now to prevent ant activity at home by following suggestions such as reducing available food and water and trimming vegetation. Reach out to Interstate Pest Management today to schedule preventative treatments and for assistance with active pest issues. Get in touch with us here or call us at (503)-832-4997.