we have millions of the little black ants at our house! Insane! I hear mint repels ants as well as cinnamon.
The garden is the one place these ants haven't found yet. You might try sprinkling cinnamon on your plants.
Let us know the outcome.
One of my reference books claims that if you squeeze fresh lemon juice across their path/trail, they will not cross it and turn around and go somewhere else. The previous suggestion of diatomaceous earth sounds like a good idea too.
Ants loath to cross lines of bone meal or powdered charcoal. Lemon juices is another deterrent if they are coming in the house. Finding their entrance, treating with the juice, and also laying down some of the peeling around the entrance of the hole can also help. So, in light of these suggestions from "The Encyclopedia of Natural Insects and Disease Control" you might try grinding up some charcoal or burnt wood, mixing it with some lemon juice and applying it at the base. If you are using the lemon juice, I wouldn't apply it directly to the fruit as it will probably damage it. If you try this I would be interested in the results.
You might also try a trap crop of tree sap. They may be drawn to it as well.
For future reference, I would suggest you post a picture if at all possible of other pest or disease problems to more accurately describe what is actually happen. You said the ants were reddish/dark brown. Try catching a few and taking a close up picture best you can. That will help me or anyone else that's trying to make suggestions for control.
Cucumber peels on ant routes will send them away for a while. If ants encounter a substance that kills them or forms a barrier, they set to work and pile up enough of each other, dead or alive, to make a bridge to cross.
Garlic fire spray will kill ants on contact... but there's plenty more on their way!
2-3 garlic bulbs (about 6-10 cloves per bulb)
6 large or 12 smaller hot chilli peppers (any variety will do, or if unavailable try 1-2 tablespoon hot chilli powder)
1 tablespoon vegetable oil
3 squirts of liquid detergent (approximately 1 dessertspoonful)
7 cups water. (Use about 2-3 cups in the blender, and top up with the rest later)
Put the whole lot into a blender and vitamize well, then strain through muslin, a coffee filter or similar. Pour what you need into a spray bottle for use and keep the rest in jars with lids on in a cupboard or on a shelf somewhere, well labeled.
Borax can be used as a natural insecticide, although must be kept away from children, pets and protect yourself too. Watch your eyes, nose, use gloves and wash hands afterwards. Borax mixed with peanut butter or something sweet, such as honey, means the ants eat it and take it back to their nest to share with other ants, hopefully poisoning all in the nest.
I have a house in SoCal... aka Ant Central. I've lived there since 1961 & the house has had an ant problem that whole time. The best I've found is to set out baits of Boric Acid (Roach Proof) mixed w/ a sweet syrup. If you mix it 50/50, it kills the ant that takes it. If you mix it weaker, say 30/70, they take it home & feed it to Mama & the kids. It keeps the numbers down & thats all that can be hoped for in SoCal.
You might also try sprinkling DE on the ground. Boric Acid on the ground is good too. Both eat at the joints of any critter w/ an exoskeleton. W/ the Boric Acid, it eats their insides out as well, but I don't know that DE would do that. I wouldn't put Borax on my soil. No... they aren't the same thing. Boric Acid is refined & not used in laundry.
I'm not sure what lemon juice would do when mixed w/ charcoal. Lemon Juice is high in citric acid, charcoal is high in whatever it is that makes it turn to lye when you wash it w/ water. I'm sure that must be highly alkaline. You'd get a very entertaining reaction... do NOT do it in a closed container!!!!! But, I'm not sure if the result would deter ants.