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Wild Costa Rica

Leaf cutting ants beware!

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Published on Friday, May 24, 2024

By Victoria Torley

After almost 12 years gardening in Costa Rica you would think I would know how to rid the area of those (insert favorite cuss word here) leaf-cutter ants.


At least not completely and not all at once.

They are sneaky little devils with huge nests and lots of workers. But I have developed some tactics to keep them at bay, so here are some tips and suggestions.

Pick your method of destruction! I am partial to Myrex and Omitox, chemical compounds that kill the fungus that the ants grow in their “gardens. They have a lot of gardens. For those of you partial to a more “natural” method, I suggest Bimbo White Bread.

Yes, bread. But don’t be fooled into thinking this is “natural” because it is the chemical fungicide in the bread that does the job of killing the fungal gardens. Both methods work and both have the same requirements. The product has to be on an active trail and kept dry. You knew there was a catch, right? Dry in our climateHere’s how:

Several large empty soda bottles, washed and dried. Make a cut leaving a canopy to keep the material dry and cover the ants as they enter and exit.

Fill the bottles with what you hope will be the ants’ favorite “snack.” Set the bottle on an active trail with the opening pointing toward the nest. Tilt the bottom up slightly to prevent water from entering and allow some of the “snack” to slip into the opening.

Place the bottle in a shady area. If you have to place the bottle in the sun, cover it with dried grass and leaves or the bottle will sweat and ruin the “snack.” You should also make sure the bottle will not roll if it is windy. Your main objective here is to keep the contents of the bottle dry and the bottle in one place. The ants will not take Omitox or Myrex if it is wetPieces of Bimbo bread may also be placed in a bottle.

How much “snack” should you use? That depends on the size of the nest. A large nest can take a kilo or more in multiple containers over at least a weekJust keep at it until you find no more foraging ants coming from the next.

Now it is a wait-and-see game. I have had ants that were partial to Omitox but ignored Myrex and vise-versa. All the ants seem to like the bread but it takes longer for it to do its work. Just get out there daily to make sure the traps are dry and keep them refilled and you should find that you can get control of the marauders.

Plant of the week
. Rosemary (S. rosmarinus) can naturally repel ants because of its strong scents. Planting this plant in or around your home can deter these sneaky invaders. Rosemary is a fragrant herb that is effective in deterring ants naturally and versatile in the kitchenIt’s a must-have for any garden and kitchen and one of the plants that repel ants that you can easily plant indoors and outside!

Rosemary’s essential oils, specifically cineole, camphor, and borneol, release a scent that ants find disagreeable. Planting rosemary in strategic locations around your garden or near entry points to your home is a reliable and effective way to create a barrier that ants are less likely to cross.

Find more amazing stories about gardening in Costa Rica on 
the Costa Rica Garden website. Regarding questions on this article, Ms. Victoria Torley, gardener columnist, can be reached by emailing


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