A little back story: First time "serious" gardner, trying to do things organically. Have had small patches before, but finally have my own land that I can put in a "proper" garden. However, there's really only one area that's suitable for that purpose and not that big of one to begin with, so moving it isn't really an option. Which brings me to my current battle with the lands original inhabitants, an ant colony.
My first strategy was live and let live, but after I found my broccoli, cauliflower, bussed spouts, beans, and half my fruit tree leaves completely riddled with holes, that wasn't a very producive option any longer. First I tried diatomaceous earth, which did work but to limited effectiveness. First I tried powdering a rings around the plants, which the ants responded to my tunneling under to the base of the plants. Then I added dusting the plants themselves, which worked as long as it remained dry. However, as soon as it rained or even had a particularly heavy dew, there is a clear path up the stem, which I've watched a literal line of ants travel up and down. Short of redusting daily, this seems to be of limited effectiveness.
Next, I stepped up to a mixture of oil orange oil. Starting with the entrances I knew about, I started spraying down the tunnels. I will say, orange oil is very effective at killing them and flushing them out. I found half a dozen more entrances I hadn't located before. However, this seems to be an indiscriminate, scorched earth approach, literally. In areas where I sprayed, I watched earthworms tunnel out of the ground and literally fling themselves into the air, writhing and eventually dying. I rinsed off the ones I saw and moved them, but I'd rather not massacre the beneficial species in I can avoid it. Additionally, seeing how extensive their tunnel network is, I doubt I'm able to penetrate far enough into it to reach the queen directly.
My next strategy is nemotodes, which a packet of just arrived today. I can't really find anything on their effectiveness on ants, but if nothing else, I'm hoping they'll cut down on the mosquitoes and gnat populations. I've considered using baits, I'm not sure of what would be effective that I would also want to have buried under my garden where the plants are growing? Does anyone have experience with this and advise on how to deal with them, short of full on chemical warfare? Thinking toward the future, are there any plants ants prefer above others that I could plant around the nest as a sacrifice to keep them away from the rest of the garden? Or is extermination the only effective option?
We have had the best success in ant control with spent coffee grounds.
We spread them all over a mound and spread them on thickly in a 3 foot diameter from the center of their active mound holes.
We have some mounds that are over 2 foot diameter, in these cases I am using a 5 foot diameter from the central entrance.
Normally it takes less than three days for them to not be there anymore.
The reason for the wide diameter is to make sure we get all or at least most of the colony.
We have had colonies take up residence in garden beds, beside and under boulders, rocks, the sidewalk to the house and just about everywhere we don't have chickens running about.
So far the only thing that works for sure is the coffee grounds and we have tried everything short of poisons.
The side benefit is that once the ants are gone, the coffee grounds help condition the soil and draw worms into the area.
I have fairly good results with nematodes for controlling (not eradicating, but greatly reducing) fire ant populations. They also help with fleas and lawn grubs. As I was reading your post I planned to recommend them. As you have already discovered them yourself, I can only congratulate you.
I've heard good things about tangle foot products. It's basically a glue that circles the base of a plant so that the ants can't cross to do things like eat your fruit on the trees. Since you specifically mentioned holes in the leaves of your fruit trees, I thought you might find it useful.
Pour a pot of boiling water directly in the ant mound.
A local guy (the dirt doctor) says molasses chases them off. I havent tried it. But....i spilled some on my driveway a week ago. I assumed ants would be all over it but they didn't show up. I think he said 2 oz per gallon of water and pour it on the mound.
A very simple and effective ant bait that I use inside the home and out if needed is as follows:
Get a few old plastic containers with lids on them-punch a few holes low and all around--
Get some cheapo peanut butter and cheapo grape or strawberry jelly.
Put about 1/4 cup of each into a bowl.
Mix in about 2-3 teaspoons of boric acid if you have it--or a bit more of the 20 mule borax powder--mix VERY well.
Put the mixture into the traps in separate piles--I usually put some wet paper towel underneath the bait in the container to keep it moist.
Take a small amount of the bait and smear a bit by the entrance holes in the container. Pop on the top.
Then watch for the ant trails. Find an active trail where they are going back and forth and put the bait traps RIGHT in the trail.
Ants, depending on the species, cannot eat with their mouth parts. Those pincers are for holding things and their actual mouths are extremely small. The bring food back to the colony and feed a slave colony of other insects that provide them with sugary nectar, which is their sustenance. The queen though, she can eat--and they bring her food directly--and if the queen dies, so does the whole colony.
All the best--and yes, the coffee ground thing works well too--just not inside the house!
The real world is bizarre enough for me...Blue Oyster Cult
So, quick update: Between the orange oil and the nemotodes, there's been a definite drop on the ant population. I've added molasses to my folar feed and I haven't seen a return of the ant trails up my plants as of yet. I also am dusting around the bases with diatamious earth once a week, just to hedge my bets.
I'll definitely be keeping the bait traps as a reserve in cause they decide to come back in force. Being that they have tunnels under about a third of the garden, would there be any concerns with the ants bringing enough of the borax underground to be a problem, being that borax is also used as an herbicide? I'm assuming not in the quantities we're talking about here, but I won't want to win the battle only to lose the war when a third of the garden dies off.
We're not coffee drinkers, so I don't have a ready supply of coffee grounds to experiment with. However, if they do come back if force, I probably could scrouge a few days worth from work and salt the earth, so to speak, in that third of the garden. I'll call this the next offensive, if necessary, and save the bait as the nuclear option.
Based on that info and looking toward the future, it might not be a bad idea to add a small amount of borax to the entire garden as a soil additive in between growing seasons to encourage the ants to move on to greener pastures, so to speak.
I'd have to do more research to find the correct dosage of course, but it does look like 20 mules has a natural, organic source of borax. So I could still keep everything organic, though that might be stretching the spirit or the term, if not the letter.
Are there any obvious concerns with this strategy, other than over doing it, of course?
The great thing about using 20 mule team borax is that it is all natural and will fit the Certified Organic requirements.
I use it and I follow a "better than Organic" protocol on Buzzard's Roost.
The dosage I use is simple, just cover the soil with enough of the powder that you can't see soil through it, no more than that is needed, and you are fine on dosage that way.
I never try to bring any low or missing nutrient up to snuff in one application, that can shock my soil biology and I have spent several years already getting it to near where I want it.
If you don't want to sprinkle the borax as a powder, mix 1 cup to two gallons water till dissolved then you can use a sprayer to apply as a soak of the top layer of soil. This method works well for already growing garden beds.
For termite and ant control I prefer the visual key of the white powder so I know where I have placed it.
If sesame is an option for your climate, scatter some seeds in the área. Sesame leaves and seeds are toxic to the fungus the ants eat. Ants don't feed on leaves, they eat a fungus they cultivate on the leaves. In a way, the ants garden.
This a controlling strategy, it will NOT erradicate them.
This seems to be working. I mixed a t (teaspoon) of powdered sugar with a T (tablespoon) of borax, I used mortar an pestal to grind it together then put a half t or so right 'round the entrances of their lil mounds and 7 days later there's about 90% reduction of them in the test area... These are sweet eating ants that are eating my jamacian cherrys and finished off the figs an work hard at chewing thru the skin on persimmons, and been problematic with other fruits... They have mounds about 3" across and a single entrance 'bout 1/8" in diameter. Haven't tried it on fire ants yet. I have tried just spreading borax around, and mixing it with granular sugar. Neither made much difference. They did a good job of picking out the sugar and leaving the borax... So... The experiment continues...