I should mention we’ve had a hot summer with a long drought.

I've seen plenty of this over years of growing Japanese and Korean lilacs. The general agreement among the people I've talked to is that it's freeze damage occurring sometime during the late fall to early spring. An opportunistic canker may have increased the severity of the injury as well. The wound doesn't present itself until the healthy part of the trunk has grown and the bark in the damaged area has dried out and started to curl back and/or slough off. So you usually won't notice it until mid-summer or later.

Worth noting, I have only seen this so far on lilac trees planted in heavier soils. This could suggest that the afflicted trees have been possibly over-saturated heading into winter.

From what I have witnessed, your tree should heal over as the top looks quite healthy despite the wound. It's basically wait-and-see now. The trees I've seen succumb to rot from this usually weren't very vigorous or healthy to begin with. This sort of injury also happens frequently on Norway maple and less commonly on sugar maple here in zone 4 Minnesota.

Thank you Ken and mntree….The tree sits in this spot next to front door. Planted 4 years ago by landscaper when we built. That side of tree with damage faces Northwest. The tree receives full afternoon sun. We moved the mulch away in picture…was a little muddy under the mulch. i watered it several times a week during the drought for a long period of time at a low flow.

We don’t see any evidence of insects although a neighbor just lost an ash tree.

Was thinking about your both of your comments…not great soil…lotta clay. The damaged side is also adjacent to the downspout. Maybe it is getting too much water? It was so dry, and then we have had some pretty good rains.

1. Should we spray it with something?

2. Should we apply some sort of tree wrap?

Thanks again for your expertise!

Unfortunately, there is not much you can do now. The tree just has to heal on its own. I wouldn't advise any kind of tree sealant as they can trap in moisture, further increasing the chances of rot developing, and slow the formation of callus tissue on the edges of the wound. As opposed to sunscald, freeze damage normally occurs on the northern half of the tree trunk and can happen even with winter trunk protection in place. That's been my experience anyway. This year I'm letting trees that are prone to this injury head into winter drier than normal to see if it makes any kind of difference. Call it an experiment, I guess, to see if over-saturated fall soil is the main culprit.

Thanks for all your advice! We will hope for the best!!