the ants are actually 'farming' the aphids (those little black sap sucking insects which cluster on the new dahlia shoots) for honeydew. If you get rid of the aphids with a blast of soft soap (Savona) or fatty acids or even a blast of water or finger squashing, the ants will go away.

I put some diatomaceous earth on the leaves.. will that help?

Do you actually see damage to the plant from the ants or are you simply concerned because the ants are there?

I did some Googling about ants eating plants and in general most people responding to the question say: Ants don't eat plants. They simply are feasting on the honeydew secreted by the plant from some other insect damage - usually aphids. The couple of exceptions might be fire ants and some kinds of leaf-cutting ants.

It's hard to tell from your photos if there is leaf damage, but I do see some little tiny things which might be aphids. They can cause a lot of damage because they basically suck the life out of plants.

Kevin

there is definite damage. and these are fire ants :(

i would not have covered such with DE ... when water would have worked ...

isnt it dusty enough down there in TX ...???

try to remember.. that ants rarely if even attack any plant ... though i will freely admit... i dont know fire ants ...

ken

It has been said ants don't eat plants, maybe they don't but they sure can topple them over. I lost a dahlia plant one year to red ants, they cut/chewed it off right at soil level. I had a good look, there wasn't any aphids that I could see just a mound of red ants. This was a mature 4 ft. exhibition dahlia plant, the blooms I was hoping to show on the weekend, needless to say the air was blue.

Annette

I live in AL, not tx. and I already tried spraying them off with water.

they are chewing its leaves offf!!

I use neem oil diluted with water in a spray bottle and douse them down good, it works great!

Fireants can be a PAIN to get rid of. They have developed an adaptability to a lot of stuff and since they are ON the plant itself, that creates another problem. I would try Cyper 8. It's an insecticide, but once dry, it is safe for pets and children, which means you can safely handle the plants once it is dry. It says it is good for ants, carpenter ants and fire brats (don't know if they are the same as fire ants), but if it kills carpenter ants, it will most likely be effective against those darn fire ants. Their bite hurts like the dickens and can easily get infected, so be careful.

Here is a link that might be useful: fire ant control

Mostly I ignore ants but If they make their hill in an inconvenient place for me then I use boric acid. I can buy it at the dollar store. I am not sure if they die or just hate it but the hill goes away. I don't mix it with water, I just shake the powder down the ant hole. I use it in the house too. A day or two later I sweep up the leftovers so I do not have mysterious white powder around my base boards.