The best thing I have found for fire ants is Amdro fire ant bait. It's granules you sprinkle around the mounds ( you don't need a lot ) They feed it to their queen. I'm sure there are other good ones but that's the one I like best. I have found that those bags of bug-b-gone or the other brands for a 100 different insects (including ants) just make fire ants relocate. It needs to be specifically for fire ants (IMO).
I don't think the fire ants herd aphids but those kind you see crawling up and down the trees do.
Avid can be bought online. You can get the generic (Abemectin) a lot cheaper. Either google avid miticide /Abemectin miticide (shopping search) or go to eBay / Amazon and search (eBay usually has best prices). It generally shows both the generic and name brand if you type in Avid miticide. When looking keep an eye out on size. You may find some Avid is cheaper but it's usually for the 8oz and not the bigger size for same price.
I mix 2 oz to 15 gal, so break that down to what ever size sprayer you have. Avid is also good for spidermites (not the eggs though so you would need an ovacide- very expensive- or spray the Avid at least 3 times 3-5 day apart), leaf miners, thrips.
You can also use Horticultural oil (ultra fine or some other brand). It takes longer to kill them because it suffocates them. I actually use that with the Avid.
