I have never encountered any problems with spirea, other than an occasional aphid attack, so not sure what to tell you. In fact, this plant has a reputation for being pretty problem-free and extremely durable! But it is a member of the rose family and is therefore prone to fireblight, but without photos, it is impossible to determine if this is your problem. Any issue with drainage?

Have you tried cutting back the plants hard in late winter just before they emerge from dormancy? Spireas take very well to pruning, even very severe pruning, so that may be an option for you to get some healthy regeneration going on.

In my zone 9b I get sporadic dieback of entire stems on the S. vanhouttei. Never could figure out why. I just cut them out and move along.

Thanks Sara & Wayne. Like I mentioned I don't remember having this bad of a problem with dieback until just more recently. What is SO strange is that when I go to trim back the dead stems, I will pull it up and then notice there is new growth on the very tip, or halfway up the stem, so I just leave that one. I have Googled this problem and find different reasons. I believe the reason for popularity is pretty flowers, which will bloom again if you deadhead the 1st ones off, nice greenery while not in bloom, and reasonable price. I probably have 10 spirea shrubs in different areas here. The one I most love is Magic Carpet and unfortunately, it seems to get hardest with die back. Have several barberry plants and love them, except for the thorns. They are a great accent color mixed with other bushes.

Thanks Garden Gal. I usually do prune the shrubs just after I begin to see new growth, to keep the size down. Didn't do that this year because there was not enough new growth. But never thought about pruning to ground to regenerate completely. Good idea. Will try that next year.

"they die back. don't know why...in the winters of west central MN, we just wrote it off to cold weather, trimmed them back, and let them regrow."

That's was my thoughts too, didn't know it wasn't a localized problem.

Some of the dead looking twigs do sprout leaves, some don't. I have been just cutting/removing the "dead dead" ones but I think next year I might cut them back completely (less work).

Thanks Bill, Yes, it would be less work and probably a good idea to regenerate completely every few years. I remember a different shrub that was close to our driveway, my hubby kept running over with his dump truck, and it would come back just fuller and prettier than ever!

And just to add, I have two, that get the sunburst leaves, 10 ft apart. Last year one looked pretty dead, I pruned it back and it came back okay. This year it looks great with no die back while the one that looked good last year is half dead. :)