Check out FAQ button on the home page.

In reality the ants are not the real problem. Ants are a necesary part of our world because they are major recyclers cleaning up after us. If these ants were in your house they would be a problem because they do not belong there, but they do belong outside. Look for other reasons these trees are not doing well.

I checked the FAQ for this forum and didn't see anything about ant control....I don't know. Maybe I missed something.

Despite some of the mind boggling weirdness that comes flying out of left field in most threads around here, it's possible that the ants could be part of your problem. That's not to say that they definitely are...but they could be. Some ants harvest the honey dew (waste) of certain insects like aphids and mealy bugs and will protect them from the predators that would otherwise control the pests. A heavy and uncontrolled infestation of those pests could cause, or at least contribute to, tree decline. There are a million other things too, but it's a possibility. If you see the ants making a trail up the trunks, there's a chance that they're at least a factor.

Did you try baits? I'm not a pest control guy but from what I've seen, people some to have the best luck with those. Baits with boric acid as the active ingredient tend to work pretty well.

It would be pretty weird for a huge colony of ants to attack some small decorative trees. Just doesn't make ecological sense. I would certainly lean toward thinking the trees are infested with something the ants are eating. Ask your nursery or extension office what infestations those particular trees tend to have and treat that to save your trees. To get rid of the ants I would vote for the boric acid bait. Although I did have success once simply dumping a bunch of powdered borax (old time laundry additive) on top of an infestation. BIG question, are you sure they are ants and not termites?????

A large colony of ants can leave the root system of plants high and dry. This is a common MO of fire ants, by the way. They are also capable of constructing huge, deep, and multi-chambered colonies. Since we are most likely not familiar with the habits and characteristics of the ant species found in ch0ban's part of the world, it might be worth considering that the ants are quite capable of killing small ornamental trees.

I'd not advise using boric acid directly on the soil. That can kill plants outright, as well! There are, as mentioned earlier, some very good boric acid baits available in the US, and I would think in other countries, as well.

Do you know what kind of ant these are?

i'll try and take a picture of them as soon as I can and post it :) It will be no problem for me whatsoever :) co'se they are ruining everything that comes near that part of the garden, and that has been happening for years....
sorry for the ignorance, but those "boric acid baits" ?? is there any way to improvise such a thing, co'se I dont think I have ever seen something like that in my stores here in Bosnia

We mention 'baits' because ants that create deep and complex colonies need to be tricked into taking the toxin into the nursery chambers and the queen, where it will be fed to everyone in the nest. You may not have access to boric acid baits in Bosnia, but I'll bet if you ask around, you'll find something similiar.

Do you have agricultural universities in your location or one of the agricultural co-operatives?