Probably an insect with an ovipositor has stabbed the tree to lay eggs in it, if so I'd think these would be expected to hatch into boring larvae - not a good thing. To find out what to do you have to get it nailed down just what happened.

hey! since you just moved in.. i am going to talk about the prior owner.. and you should take none of it personally ... looking at the first pic.. i see nearly no landscape ... and i am going to bet.. they bought a rather large transplant.. from the bigboxstore.. a few years back.. planted it [i too wonder if it is telephone poled .. no root flare at the ground] ..... i am going to guess ... it was pot bound.. and they did little than dig a hole and stick it in .. and water it at planting .. i am further going to guess ... that they did little if no PROPER followup in regard to PROPER WATERING .... for the 2 or 3 years a large transplant would require ... plus throw in drought if any over that period ... all that resulting in lack of proper moisture.. thru the ensuing few years ... resulting in sunscald.. on the south facing side of the tree ... and if all the above were true.. improper pruning leading to.. or complicating more bark damage ... there!! .. that is just about everything i can think of.. as to what might have caused the problem ... BTW.. ants DO not harm an otherwise healthy tree ... at worst they mess with other bugs.. 'milking' aphids of honeydew' e.g. ... and for sure.. a couple means nothing.. they are just surveying their domain ... what can you do??? .. not much.. trees heal themselves.. if you can restore vigor thru proper watering.. "feeding" it.. will not make a difference.. it is not a child ... besides the fact that the rather weed free lawn tells me.. it is probably fertilized ... so the tree needs nothing else ... if vigor were to return.. it can heal itself thru compartmentalization .... [thats my long word for the day ... lol ..] but if the tree is not proper for your area.. as noted above.. whats the point ... be done with it ... cut it to the ground.. do your research for something new.. and plant it a few feet off to the side ... unless you really want to find out what is going on underground.. simply for the sake of knowledge ... then dig it up.. so you can replant in the same hole ... good luck with your new house ... presumably.. you redid the interior to your taste.. so lets redo this tree.. to your taste.. rather than spending the next decade.. 'dealing' with it.. ken

I started a thread in the Trees forum (link below) about some damage I've recently seen with my shamel ash trees. Thought I'd post here as well since maybe others here in AZ have seen this kind of damage. The original post has a link to pictures. Here is a link that might be useful: Trees forum post

Tor, I'd like it better if that paper dealt with other canker types. This is almost surely not Cytospora canker on this tulip tree. Far more likely to be Nectria. I see from a quick search that some experts do recommend "cutting it out" while still small. I don't see that as a reasonable option in this case. Cutting out a sizable notch in so large a tree seems like a Pyrrhic solution to me. In any case, I remain open to the idea of treating it....just not sure yet what that might consist of. What we do know about such cankers is that A) They are serious and B) In some cases, a healthy tree can simply "outrun" them. As this is obviously a great tree, I'm hoping for the latter. Right on my street, there used to be a very large ash tree. I'm talking mammoth. I suppose it was well over 100 ft. in height with a very straight, branch-free trunk for much of the way up. In any case, that giant tree had a canker on its trunk similar to this one. I'm sorry to say, the decision was made to take the thing down. Upon examination of the wood in the area of the canker, there was no additional infection, no rot, no discoloration of the wood. I think we goofed. But you really can't tell by just looking at it.