Wow, I've never seen red ants on a fruit tree before, and we have lots of fruit trees. Normally, if ants are on a fruit tree, that generally is a sign that the fruit tree has some other problem---normally aphids (the ants are attracted to the honeydew the aphids produce) or scale insects. So the first thing I'd try would be to carefully check the trees (look on the undersides of leaves for aphids) to see if I can see something else that is attracting the ants. Then, I'd address whatever I found. Also, look at the place where the ants are feeding and see if there is a sticky substance there (that likely would be the honeydew from aphids). If there is, you might try to wash it off.

The best products I have found for ants are organic products that contain either Spinosad or Avermectin in them as their active ingredient. The ones I use are in baits that the ants ingest, and I use two different ones. I use an ant control bait containing Spinosad (the one I generally use is called Come and Get It, but I've used a different one by EcoSense too) for fire ants that get into the raised beds in my fenced-in veggie garden plot. Then, for the carpenter ants that devour wood, I use a product called Advance that contains Avermectin/Abamectin. You'd have to check the labels to see if they can be used around fruit trees. I've never had to use them that way, and don't remember what their label may or may not say about it. If they can be used around fruit trees, you could scatter the bait product on the top of the soil around the trees.

Another solution would be to first use a sharp stream of water from the hose to knock all the ants off the trees. Then, immediately after that before they can climb back up into the tree, apply Tree Tanglefoot to the trunk of the tree. They'll get stuck in it (hopefully) and that will be the end of them. You can sometimes find Tree Tanglefoot in nurseries or garden centers, or can order it online. I'll link some so you'll at least know what the packaging looks like:

Tree Tanglefoot

Instead of Tree Tanglefoot, some people attempt to get the same effect by wrapping duct tape around the tree trunk with the sticky side out in the hope that the ants will stick to the duct tape. I don't know how reliable this method will or will not be.

Sometimes you can address fruit tree pest problems by spraying the tree with a summerweight, superfine oil (a lighterweight equivalent of the heavier dormant oil). Do your research carefully on the temperatures at which summerweight oil can be applied, because even though the company says it can be applied in "hot weather", I am not sure I know what their definition of hot is. Sometimes in gardening discussions, companies say something can be used in hot weather, but they don't really mean it can be used in our kind of hot weather. Spraying the tree with an insectical soap following label directions might work.

You also might have luck spraying the ground around the trees, and maybe the outside of the containers the trees are in, with a peppermint soap/water spray. Ants follow a scent trail left by other ants and the peppermint spray interferes with their ability to smell the scent trail and follow it. Unfortunately, this only works until rainfall or irrigation washes away or further dilutes the soap spray, so it is not a long-term solution. The brand of peppermint soap I use is Dr. Bronner's. Be careful to not apply too much soap. I use 1 tablespoon per 1 quart of water. Soap is not only a good pesticide in some cases, but it also is a herbicide at higher ratios of soap to water.

Good luck with your ant problem.

Dawn