I had a same kind of damage occur once to a Cycas revoluta. At the time, I also thought of sealing up the injury, but apparently, the latest thinking about this kind of damage is not to seal it up but let it be exposed to sun and fresh air and its drying effects. I also had the problem with the ants moving in, actually it was the ants that indicated a problem because I hadn't even noticed the rotting section of trunk near the surface of the soil (apparently a risky area for rotting among cycads). I would suggest you maybe dust the wounded area with fungicide. You've already cleaned out the wound with the ants--hopefully they won't return but the risk remains for some kind of infection to start in that crevice. Visit your local garden center and maybe they can give you further advice.

I would leave it open also. Silicon will not stay in the hold anyway for any lenth of time. There are some other things that might seal it like the material that is used to seal electrical pipes on the outside of buildings. It looks like clay but stays put pretty good.

I believe Home Depot sells a wound tree spray. Its in an aresol can by Ortho called Pruning Sealer....we use it when we cut a limb off a tree, I'm sure it would be perfect for your problem.

Correct me if I'm wrong, but don't most horticulturalist now advise AGAINST using any sealers and to let the wound heal naturally??

Palms cannot heal themselves like deciduous trees and wounds can lead to other problems. I've seen large palms with trunk damage and they seem to be doing fine but this hole works my nerves and then there are the ants too. The tar type tree sealer mentioned above was also suggested to me by a landscaper. I've used that before on trees in Michgan, I'll try it on the palm.

I understand what you are saying. As I said, I had this similar situation happen to a cycad of mine in the past. (ants and all). So I did some reseach and learned that most horticulturalist today advise against using sealants such as tar or anything else--don't recall any exemptions for non-deciduous plants such as palms. Would be interested in hearing what the professionals are currently saying these days in case this occurs in my collect again. Good luck!

I picked up some pruning sealer at the local nursery. I removed the silicone that I had filled the hole with a few months ago only to find that the hole was much shallower.
I sprayed the sealer on the area. I'm sure the palm will be fine.

I have the same exact problem in a 15' foxtail and was hoping that reviving this thread could lead to some answer. I have 2 other 15' foxtails without this right next to it and a triple 15' on the other side. My main concern is a fungus or insect that will infect the rest of them. They appear as slits that are narrow but about 4" tall with about 4-5 of them right next to each other. Tap on the area and out come these little tiny light colored ants. Located in SE Florida, damaged area faces directly north with nothing blocking it. I can post a picture but am unsure how to.

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Just go to photobucket and upload your pics then use the hotmail link in your message box your picture will automatically appear .

I also have a hole in the trunk of my 15 ft adonidia palm, but without the ants. It is about 10 inches above the base, and is a vertical slit. The area around the hole is black and so is a large area between the hole and the roots. There is further blackening along the same side of the trunk up to the growing fronds. Does anyone know what this is? I have other adonidias nearby and the wound faces south.

The hole could be caused by a woodpecker looking for bugs to eat. Woodpeckers have also been known to make a hole and then come back latter looking for any bugs that have moved in.
Unlike other trees that have pith wood surrounded by a cambian layer, a palm tree's trunk is a mass of fiberous tubes; all delivering nutrients from the ground to the leaves for photosynthesis. Damage to some of the bundle won't hurt the rest of the bundle unless an infection takes place. I think it best to leave the wound open and occasionally sparay it with a fungicide or at the very least something like Physan (if they still make it.)