Thanks for the tips, everyone. I'm not sure what grits are or if you can buy that up here. Does it have another name? What is the molasses/sugarwater ratio? That sounds like something I might want to start with. I found more results of why NOT to use Borax than those that recommend it, so I'll give that a pass. Good point about "what are they eating". What are they eating? I ought to spend a while following their trail to check that out. Interesting, though, is that when you look closely at the colony, you don't see dozens of them scurrying around, as you would with the little brown ants. You actually have to look close to find them. Maybe it's just a very old colony? I ought to take a picture but my neighbors probably already think I'm a little soft in the head for staring at my plants so much. (It's a PLANNING process...)

It's obvious to me that the people who claim ants do not kill trees have absolutely no experience with fire ants or any knowledge of them....I've noticed they are all from more northern states than Florida. Yes, certain ants will kill trees. Fire ants kill trees and shrubs. They are a horrible scourage here and were imported from Brazil in the early 1900's into Pensacola via cargo ships. They are one of the most miserable creatures on earth, and a prime example of how careless importation of foreign species is so disruptive to another area. In Brazil there is a fly that keeps the fire ants in check there, and then other birds and animals that keep the flies in check, and so on. Here, our native species do not know what to do with them, and they have flourished and gotten out of control. This is all information given to me by our local extension office. They have become so bad since the last tropical storm on our property, (and other properties in our area that did not flood), that I can't garden or walk to my clotheslines without being bitten. The bites are horrible. They burn, sting, and itch all at the same time, and then the bite forms a nasty pustule. Imagine having 50 bites. Imagine a tree or shrub dealing with them. We are having our farmer's co-op come to treat our whole 10 acres. They are not just present at the mounds. They scout all over the place. Our property did not flood, unlike many unlucky people in my area, so the fire ants have migrated to properties that stayed dry. They literall float mounds of themselves on top of flooded areas. I saw it with my own eyes. They have killed 7 rose bushes on fortuniana root stock, 5 citrus trees, and several of my native holly trees so far since the storm. They eat the roots and they bore up into the trunks of the trees. Once established into and near the trees they are almost impossible to get rid of. I've tried everything, including drenches. I am going to have my husband pull them with the tractor and burn them. Since the roots are so damaged I could actually easily remove them with a shovel, but I won't go near them any more. In addition to all of this it appears that they have displaced many of our native ants, who do not bite, and whom are important to the balance of our ecology. They've even appeared to have eaten all our earthworms. I can't find any in my composted areas. So, unfortunately, we have to "nuke" our whole property and then try to introduce the beneficials back in. So yes, ants may have killed the original poster's tree.

This is tricky. You do realize of course...you are going to continue to deal with suckers? The long term solution is to just replace the poplar with a better tree for house-shading. As for the leftover stumps, the right concentration of the right herbicide could certainly manage to just kill the left over stumps and minimally impact the mother tree. But there are far too many variables to recommend an approach. The wrong concentration of the wrong herbicide could certainly seriously damage the "mother tree". You haven't even told us how far away they are. If it were me I might try to spray the foliar _regrowth_ of the stumps, with a standard strong glyphosate _spray_ mix, say 5%. Which would ordinarily kill similarly sized seedlings. Unless the suckers are very close I don't think it will affect the main tree, but I can't guarantee it. Especially because I have no experience dealing with poplar as a weed and don't know about the specific level of sensitivity it has. It could be especially sensitive to glyphosate, or not. (Legumes, for example, are incredibly sensitive to triclopyr, and I once almost killed a Kentucky coffee tree seedling just by spraying some Oxalis about 1' away from it with a typical spray formulation...nothing too concentrated. There was definitely no direct contact, it either happened due to vaporization or triclopyr residue in the soil.)

Ed, I would agree with you that whatever gets buried has a good likelihood of being impacted or killed. However, I would strongly disagree with you that we are talking about killing half of the tree's roots. My opinion is that half (maybe more like a third) the tree's roots were affected/killed when the house was initially built and the yard was initially terraced. I have read conflicting things on poplar tree roots ( I read up on them a while back since I have two 2-foot-wide-dbh poplars flanking my house.) One thing I read was a study where they looked at pole-sized poplars and found that the poplars have a lot of roots rather close to the tree, and not a bunch of radial and evenly spaced feeder roots. I have also read that poplar roots can extend anywhere from 160 to 490 feet away from the tree. I am assuming that the area on the other side of the tree is either forest, or backyard of another house. My assumption based on this is that when Brian's house was built and the yard graded, the poplar was definitely affected, so it overcompensated the root loss on the upper slope by creating more feeder roots on the lower slope to get more moisture. As an aside that I won't get too much into, and that you may already know, there is emerging research that trees are connect by a mycorrhizal fungi network via their roots, and trees can actually share and transfer nutrients. The larger trees tend to be “nodes" in these networks. Because of this tree's size, my guess is that it has a lot of ways to get nutrients. That being said, obviously less damage is the most preferred option, and getting someone to bobcat away all if the terraced soil would probably be best. That sounds like it would be a lot of money, but maybe somebody nearby needs a lot of fill dirt for free.