I have some very otherwise-healthy balsams in my yard, started them from tiny bare-root stock and they've done pretty well. About a year ago, a few tips of the branches (about 4 inches or so) started turning brown near the base. I figured it was some animal urinating on them or just age. But then this year, the same thing started happening randomly all over the tree. After the rains we've had, believe me, it's not browning from lack of water. And throughout last year's drought, I trickle-fed them all summer long and they actually grew well.

I examined the tips closely after removing them and found that each one had a little vertical incision in the stem, as if some pest had laid eggs there. I know that cidadas can do a similar thing, but these stems are very tiny and we have not had cicadas yet this year.

Any ideas out there what the pest is and how to eradicate it? It's only happening on the balsams, I have tons of other conifers on the property, (spruce, cedar, redwood, thuja, concolor, etc.) nothing else has been affected.

Would love some feedback or opinions on this.