Re: Walmart products. Of course every Walmart could have some different products - but in the ones that I frequent, I have never seen any organic products, only the chemical products which I wouldn't use, but that is just my opinion. In our area, the Home Depots have started carrying some organic products. Many garden centers carry diatematious earth - maybe even Walmart!!!
Re: beneficial nematodes - we can get them here in our local organic gardening stores, not sure about the Carolinas - but I found an online site where you can read about the nematodes and they ship - it says free shipping - I do know they have to be kept cool, for example if you are not going to apply them when you buy them, they have to be kept in the refridgerator till you put them on the yard - so I would ask about this before getting them shipped - because if they get too hot (before they are put on the yard) they will die.
This site also has nematodes in amounts for yards (square feet) or farms (acres). It looks like a completely reputable site - but I would ask about how they are kept cool during shipping.
http://store.arbico-organics.com/org...nematodes.html
Also, for non-nematode fire ant control - an orange oil drench will do the trick - yep, the same orange oil that is used in cleaning products. You can buy the garden strength of orange oil, mix it with water and pour it on the mound and it will kill the fire ants. Boiling water into the mound will also kill most of the ants, but maybe not the queen, if she is really deep - any surviving ants will usually move though - although it could be to a different spot in your yard!
But I promise you that if you use beneficial nematodes, you will not have any fire ants in your yard. I've been using them for 5 years and have not had one mound. Before nematodes, mounds all the time.