Argentine Ant Management
Home and Landscape
Exclusion and Clean Up
Locating the Nest
The Boiling Water Method
Ants Indoors
Exclusion and Clean Up
When you see a trail of ants indoors, don’t panic. Before you do anything, use the trail to figure out the next steps. First, follow the trail to find the opening they’re using to get into the room. Next, seal the opening with caulk, this is exclusion. Then, identify whatever food the ants found, remove it, and wipe up the ants and clean the area with warm soapy water or a household cleaner.
Household cleaners may kill living ants on contact. But I do not recommend using household cleaners for the purpose of killing ants, as that would be an off-label recommendation. And, doing so will not solve the bigger, recurring ant problem.
Cleaning up with soapy water or cleaners does have the added benefit of eliminating the ant’s chemical trail. Therefore, if other ants find another way in, there will not be any old trails for them to use to their advantage. They’ll have to start over and rely on random searching. The hope is that they won’t find anything and return to the nest with nothing to share.
The final step is to go outside, near the point of entry you caulked inside, to find the breach the ants are using to get into the walls. Seal that up with caulking as well. This will slow them down, but just for a bit. The real work starts out in the yard. We have to reduce the number of Argentine ant nests outdoors to have a lasting impact.
Key points for managing ants indoors
Follow the ant trail to see where they’re coming in
Exclusion - seal the opening with caulk
Clean up the ants and eliminate their chemical trail using warm soapy water or a household cleaner
Exclusion - go outside and seal up the cracks the ants are using to get indoors
More work must be done outdoors for best results
Ants Outdoors
Locating the Nest
There are options for dealing with ant nests outdoors that can provide swift results, but will ultimately also require long-term maintenance. The options you choose depend on personal preference and the time you’re willing to invest.
To reduce the number of ant nests outdoors, locate the ant nests using one of two methods. One method is to find ant trails and follow them to locate the nest opening.
The other method is to use a garden hose. Argentine ants like hardscaping. They’ll excavate their nests under rocks, posts, railroad ties, bricks, cement slabs, etc. Use a garden hose to apply a stream of water along the borders of flower beds, raised beds, patios, decks, etc. If you hit a nest with a stream of water, wait a minute and a small portion of the ants will likely scurry out. That’s your indication you’ve found an underground colony - a nest.
Can we just drown ants? No. Using a garden hose to drown an ant nest won’t work. As the video explains, ants have evolved to survive severe flooding. Using a garden hose will only cause them to spread out and find new nesting locations. Therefore, the garden hose should only be used for discovery; the process of locating ant nests.
When ants do emerge, there may be dozens to hundreds hustling to get away from the perceived flood, but this can quickly become a secondary problem.
Our job at this moment is to quell the escape behavior and make it difficult for the ants to spread out and find new places in the yard to start new nesting sites. One option is to use a contact, topical insecticide. There are many products available at hardware stores and nurseries and many use essential plant oils instead of synthetic chemicals. Choose whatever product you’re comfortable with and always read the label and follow the instructions for use.
Pros and cons of contact sprays
Pros:
This is a fast way to eliminate ants quickly, on contact.
Cons:
Safety issues, read and follow all label instructions
There will be many more ants below ground that are not impacted by the above ground spray application. For that you need to begin nest elimination, especially targeting the queens.
Nest Elimination
The Boiling Water Method
Now that you’ve discovered the nest sites, and quashed the runaways, the next option can make a lasting impact on ant populations. The boiling water method. This method can provide swift results, but must be done with great care and caution. See below for important precautions regarding personal safety and damage to non-target organisms and surrounding vegetation.
The boiling water method has been a home remedy that I’ve known about and have successfully used against Argentine ants for decades. Research was conducted in 1980 to test this method against fire ants, A Simple, Non-Toxic Remedy Against Fire Ants, and was proven to be very effective. Similar research on the use of boiling water to manage Argentine ants has not been conducted, but the methods and outcomes appear to be the same.
To be effective, the boiling water method requires that nests are located first. If you choose not to use an insecticide spray as described above, have the hot water ready to go before using the hose method to locate the nest.
This method requires a total of 2-3 gallons of boiling water and a previously identified ant nest. The water is directed, as a trickle, down into nest openings. Argentine ant nest openings are typically flush with the soil surface and can have a cluster of openings at the main entrance area. The slow trickling water must be confined to the nest openings. If done correctly, there will be little runoff as the network of ant nest tunnels will allow the water to seep into the sectors of the nest, including those occupied by the queens and the developing young.
Each nest requires an additional treatment of 2-3 gallons of boiling water. This method can eliminate a major portion of nest occupants and slow the colony’s growth.
Alternatively, baits can be used as a stand alone method for nest elimination, and there are no real negative side effects. The challenge is that it takes much longer to achieve lasting control. See below for more information on baits.
Pros and Cons of the Boiling Water Method
Pros:
Has the potential to eliminate a large portion of underground nest occupants, including the queens and developing young
Cons:
The potential for personal injury, including burns, when handling boiling or scalding hot water
The potential for injury to non-target organisms and nearby plants and root systems
Important considerations if using the boiling water method for Argentine ant control
Safety - Handling and pouring boiling or scalding hot water poses risks of burns to the user, others nearby and non-target species. Use caution and common sense. Wear protective clothing and footwear if you choose to use this method.
Vegetation damage - If the ant nest is located in an area with vegetation, the hot water may kill roots in the vicinity where you are pouring. However, since you will be slowly dribbling the tiny stream of hot water into the nest opening, the water will be flowing down the tunnels into the soil and there’s unlikely to be significant root growth within the nest itself.
Location - Argentine ant nest elimination with boiling water can be easier if they are in open areas outdoors, for example, in a flowerbed vs under hardscaping or concrete slabs. If the nest openings appear to be under a driveway, porch or other structure, look for cracks or seams and use those areas as access points for the hot water. Do not use this method indoors.
Be Thorough - Use the hot water in a slow, small stream to allow for better penetration and better targeting of queens within the nest. However, the process will have to be repeated until you have applied a total of 2-3 gallons of water. Then, you will need to follow up and check the nest after two weeks to see if there is any new activity. If so, treat again. Additionally, you must treat all the nests in a yard space that you can find and access, as ants from nearby nests will repopulate abandoned nests.
Non-target effects - What about native ants or other potentially beneficial insects? Argentine ants are territorial. Therefore, native ants or other beneficial soil dwellers are unlikely to be in the area. The hot water should be directed down the nest openings, not spread out across a wide area, to reduce or eliminate the impacts on other species.
Ant Baits
Ant baits can be used as a stand alone method for nest elimination if you choose not to use the boiling water method described above.
Ant baits are a good, long-term, effective, less hazardous, hands-off approach to Argentine ant control. However, using baits alone will take much longer to see results. The key to success with baits is diligence. Stick with it, be consistent, and don’t give up.
There are a variety of outdoor bait stations available from hardware stores, nurseries or garden centers. Read the label to make sure they contain 0.5 to 1.0% solution of borax along with a sugar/sucrose solution as a carrier. Argentine ants love sugar and this type of bait works best for them year round. The mode of action for borax is to disrupt the ant’s digestive system. You can make your own DIY borax bait to use, but you will need some type of station for dispensing the formula which might be challenging to figure out. There are many ant bait products on the market right now, but again, I’m not endorsing any particular product or brand. You can choose which one you want as long as you understand what the ingredients are and what they do because there are baits that use ingredients other than or in addition to borax, such as synthetic insecticides. For any type of bait formulation, use as many stations as you can afford to eliminate as many nests as possible. Having between at least one 1 and up to 4 stations for each side of an average sized home is a good target range.
See UC IPM for additional information on ant baits.
I have used a different DIY formulation for Argentine ants that you can make at home and does not require a dispensing station. This is a formula I learned from a pest advisor colleague, it has not been researched or scientifically validated in any way. But I’ve used it successfully, so here it is.
In a small bowl, mix 4 parts honey and 1 part baking powder. The baking powder mode of action disrupts the ants digestive system, similar to the borax. Once you’ve found where ants are nesting or coming into a home or building, you can apply small amounts (about a tablespoon) around the area. As the bait diminishes over the next few days, you’ll need to mix a fresh batch and reapply.
With all baiting programs, you’ll need to stay diligent. This will be a weeks-long or months-long project. Keeping the bait supply in good order and making sure the ants keep taking it is the key to long-term success. Otherwise, the ant numbers will bounce back in no time. To keep ant numbers suppressed means maintaining a baiting program, possibly for years.
How it works: Whether you use a commercial or DYI bait, the process of ant elimination is the same. You’re taking advantage of their use of trophallaxis to spread the toxin throughout the nest and eventually to the queens. The ultimate control of Argentine ants occurs by eliminating the queens. The toxin is at a low enough concentration in the bait that it won’t repel or kill the forager as it is bringing the bait back to the nest. It just thinks it's another great source of sugar. The recruitment process will start and more and more ants will visit the bait. But the toxin is strong enough to eventually have an effect on the developing young and ultimately the queens.
Do not purchase baits formulated for red imported fire ants to manage Argentine ants. Fire ants have a different biology and the products are specially designed and formulated for them as the target insect. Again, always read the label and follow the directions for use.
Pros:
Baits can be used as a stand alone ant control method, but it does take time
Fewer non-target and safety concerns
Cons:
Baits are expensive to replace as often as will be needed
They are slow acting
This is a long-term commitment
Maintenance
Once you have reduced the overall ant population around your home with boiling water or baits, it is time for long-term maintenance. And this is a job for baits. For long-term maintenance you can reduce the number of bait stations you used for elimination purposes, but keep at least one or two in areas that you now know are prone to harboring ant nests. Check them every two weeks or so to ensure they are in good order and to keep tabs on ant activity. If the number of ants shoots up again, you can either spot treat with the boiling water or ramp up the number of bait stations until things get back to manageable levels. Like I said, this is a commitment. Pest management is rarely an easy, one and done, walk away and forget it kind of exercise.
Additional Exclusion Methods
Using caulk to seal openings used by ants is a must. But you do not need to seal up every crack and crevice into your home. That’s an unrealistic expectation. Instead, just seal up any cracks the ants are currently using. Let them show you which ones allow them access, instead of you trying to guess. This is an important step because even though you have sealed up interior access points, Argentine ants will set up temporary nests in wall spaces of your home and from these satellite nests they will relentlessly seek out new ways to gain access to food and water in the home. Caulking outside helps prevent the establishment of these interior wall nests.
Sources
Argentine Ant Biology and Management in Southern California Citrus Orchards, UC Riverside
Tschinkel, W. and Howard, D. A Simple, Non-Toxic Home Remedy Against Fire Ants. J. Georgia Entomol. Soc. 15(1), January, 1980, 102-105.
In the landscape, Argentine ants are notorious for infesting trees and shrubs, especially fruit trees. Often, our landscape plants host a variety of insects that feed on plant sap, like aphids, whiteflies, and mealybugs. Argentine ants love these insects because they secrete a sugar laden fluid called honeydew. The ants harvest this honeydew, along with nectar from flowers and sugars from rotting fruit, and bring it back to the nest to feed the colony. Products such as Tanglefoot can be applied to tree trunks to create a physical barrier to prevent ants from making their way up from the soil into the canopy. This exclusion technique also requires regular maintenance. As ants attempt to pass over the sticky barrier, they get stuck and perish in place. Once enough ants die, they’ll create a non-sticky walkway, a bridge of sorts, that other ants can use to get over the barrier and to the desired resources up in the tree.
Plants and trees that touch homes and other structures provide another type of bridge for ants to travel from the soil, up the plant and to the structure. Walk the perimeter of your home or other structures to see if any plants or trees are touching the walls. Simple pruning of plants, including nice two-level shrubbery designs, around the home will create the needed space between vegetation and the walls, and is very much worth the effort. So much so, consider adding this task to your seasonal home maintenance list. Using a combination of Tanglefoot and trimming is effective exclusion for keeping ants at bay in outdoor settings.
Key Points for Managing Ants Outdoors
Follow the ant trails or use a garden hose to locate nests
Have a strategy for eliminating the ants that scurry if using the garden hose, otherwise the surviving ants will simply relocate and find new nesting sites
Choose a strategy for nest elimination that will eliminate the queen and developing young
If using boiling water - proceed with caution, go slowly, and be thorough
If using baits - monitor the condition of the ant bait weekly, replace as needed, stay diligent
Use baits long-term to keep ant populations low
For exclusion, apply Tanglefoot to prevent ants from climbing up into tree canopies and trim back any plants touching structures
Monitor the condition of Tanglefoot and replace as needed and inspect plant growth regularly and trim as needed
Congratulations! You made it to the end.
If you now find yourself fascinated by ants and want to learn more, check out these entomologists who’ve specialized in studying ants. Ants are their obsession!
Brian Fisher, Deborah Gordon, Corrie Moreau, Mary Talbot, and E. O. Wilson
DISCLAIMER: We assume no liability for any accidents, injuries or outcomes if you choose to use any of these methods for ant control. Follow all safety precautions and instructions for use on labels for whichever products you buy. The information in this blog should in no way be considered a guarantee of outcomes, real or perceived, intended or unintended. Injuries to any persons resulting from the use of any product or method are the responsibility of the user. Always read and follow the product label for specific instructions on application rates, timing, and precautions.