I have been waging a war in one particular apiary where I keep about 50 -100 nucs at different times of the year. ...and I have a HUGE ant problem.
I didn't always have this ant problem. 5 years ago, there were fire ants on the property, but honestly, I never had a problem with fire ants. They were more of a nuisance that I could get rid of if I had to. But over the last 5 years the familiar fire ant mounds have all disappeared. Now, my land is absolutely infested with what I believe are Argentine Ants. I haven't had it identified for sure, but that's what I believe they are. They don't make mounds, or at least not big ones, every so often you'll find a tiny little ant mound that they've made. But the ants are everywhere. I can walk out to any square yard of the 10 acres this particular apiary is on, look down, and find ants crawling everywhere.
I've used very basic hive stands, which are composed of cinder blocks, and 4"x4"x8''s. It's works, is mobile and cheap.
This was the first year that I believe, I've lost nucs to these ants. They relentlessly harass the hives, weak and strong alike. But keep in mind I'm talking 5 frame nucs, so, not a full strength hive. Often I'll be making splits, so I'll have even weaker nucs. The ants will form long columns into the hive, and since these are tiny ants they'll find a way through the tiniest crack.
Here's what I've tried:
Diatomaceous earth, I brought in a few hundred pounds of the stuff and covered the ground with it. If it worked at all, it was short lived. I've watched the ants crawl right over it, and after it rained once, it's no different than clay.
Essential oils: LOL no effect. Someone suggested cinnamon, but I'm talking a large yard, if it loses it's effectiveness after a rain, I can't afford the time and money to keep that kind of attack up.
High temp axle grease. I smeared this muck in an unbroken circle around the cinder blocks. It was a long and laborious process. And it made a nasty mess. But it seemed to work for a few days. While visiting the yard I noticed the ants crossing the stuff. When it was fresh they made a bridge across the grease barrier with their fallen brethren. A dead ant bridge, if you will. The grease became caked with the dead ants. But then after a week or so, I noticed the ants didn't even need the dead ant bridge to cross the grease. They were walking right over it the grease itself It appears to have degraded, or formed a layer (dry membrane?) they could cross. ....what an ineffective mess the grease has made. But I didn't give up on it. I looked at some of the hive stand designs that use an upside down bell to contain the grease, and devised a similar strategy that might work on my cinder block stands.
I found some aluminum foil pans that where about 1" deep, and overhung the cinder blocks about 1" on all sides. I turned the pans upside down on the top cinder block, and caked it full of the high temp grease. Thinking that perhaps this would shelter it from rain and sun, and might make it more of a barrier to the ants. .....again, it seemed to work for a few days but after a week or so, the ants where moving right over these barriers.
So much for mechanical grease barriers.
The next thing I tried was bait traps. I googled around and found different recipes for making ant traps using 20 Mule Borax. I bought a case of these little pint sized sealable tubs from a restaurant supply company. I drilled ant sized holes around the top, so the ants could get in while keeping the bees out. I made up several hundred of these traps, and placed them in the hollows of the cinder blocks.
Eureka! ...I thought.
For the few weeks the ant problem seemed to have gone away. But while checking on some splits, I noticed the ants were back. So I gathered up all the traps, washed them and put in fresh bait. Again, the ant problem seemed to decrease. But today, the ants seem to be building up strength again. Collumes of them going into different nucs.
I'm really pulling my hair out on this one. In all my years I've never seen anything like this. I'm going to continue using the traps because they are the most effective method I've tried so far, but I'm open to more ideas.
Does anyone have anything more than...
Grease mechanical barrier hive stands
I'm at DEFCON 1 on this ant problem. I'd be willing to try anything.