Folks:

First time posting (long time gardener, so I'll be back). Could someone please tell me what they think is going on with my Raspberries?

These fall bearing berries that I planted in 2016. Past 3 years have had decent production, but not excellent. I noticed some of the tops of a few (maybe 20%) of the plants have dying leaves and even just the top of the stems.

They get adequate water; dripped every day for 10 minutes via dipper line (not hose). They have had bees going nuts for 3 weeks and now have fruit developing (small but there). I've fertilized them twice this year but haven't treated them for any bugs or fungus. I also gave them two treatments of Iron as they had an issue with that last year.

I sure hope this isn't a virus about to destroy my plants. They are in a single row about 12 feet long. We live in Utah, so it's dry here and fungus isn't likely an issue--but what do I know.

Let me know if folks need more pictures or closer.

It's not leaf curl. It looks like the leaves had been damaged when they were very young and whatever caused it is long gone: the new shoot at the top looks normal enough to me. If you are really worried about it just prune the plant at the first normal-looking leaf and forget about it.

One thing about irrigation: while in Utah you will never see the same yields as, say, Coastal Oregon, you need to improve your watering technique.
Raspberries actually need much more water after getting established (second/third year) and prefer regular deep watering. The chlorosis you saw was most likely tied to your pattern of daily but shallow irrigation: we had exactly the same issue with currant back in the days.
Personally I would run the drip line at least thirty minutes every three days. In case of drought or very high temperatures you may want to water for 25/30 minutes every other day.
I am not a fan of conventional mulching but you may want to consider plstic mulch sheets to help keep soil moisture and temperature under control.

My new shoots are healthy but the damage continues. Probably 30% of the plants have this happening. I've found no bugs yet so I'm clueless what caused it.

Look for two sets of healed wounds around the stem close together: if you find them, it's a cane borer.
The timing is about right for the eggs to hatch and the little larvae to start wreck havoc on plants.

ElPolloDiablo:

Fascinating. I have 4 videos to show you, but I can't post links to my youtube yet. Hopefully that can be removed soon since I filmed the actual larva I found. I filmed me cutting into them and finding a larva. So that's likely it. Although I don't have the rings, as described, I do have a darker brown spot below the dead areas . I cut into that brown area and found a large larva. Moving and clearly alive. Yuck.

Here are two pictures of the larva that I discovered. I'm now trying to determine if they are Raspberry horntail, Crown Borer or
or Stem Girdler.

From my reading, I believe I have Raspberry Horntail issues. Not much I can do but remove the damaged primacane tops



It appears all I can do is remove the damaged tops, and low enough to capture the larva. Also, since mine are everberring (Carolina varity) I should cut all my canes to the ground in February. This will avoid the larva from emerging--if they made it to the bottom in this year. Last year I first year primocanes winter over. Perhaps that is part of the cause.

Cane borers, that's them alright.
The standard method to get rid of them is to cut the affected canes about 1" above the node closest to the ground and burn all the cuttings. That should teach them.