Spirea

My spirea has been robustly growing for about 9 years. (I'm sorry I can't be more specific than "spirea" although it resembles the garland spirea in both leaves and blooms." This summer it is blighted. It's received enough water, but we've had a particularly hot summer for our area, with heat indexes over 100 for quite a few days. Should I be looking for insects, perhaps using a fungicide, fertilizing like crazy?
Hopefully you can make out in the photo that over half the plant is without leaves. I'm not sure that the canes themselves are dead, though. They were not as brittle as I expected when I cut into them, and I saw some green.

Spirea can get leggy and not look so good. If the stems are still green, you can cut it back to about 8". I cut mine back mostly in the spring, but in your zone there's still time for it to start growing again. You'll see new green sprouts along the cut stems in a matter of days. It will bounce back and be a nice looking shrub again, back to it's original size.

I cut this one back and moved it about 4 weeks ago. It was too close to the patio and I needed the room. It's doing fine after transplanting and cutting back. In it's original spot it would have grown faster, but I had to deal with transplant shock also.

Thank you. Yet I believe this shrub is beyond leggy. It's hard to see but on the almost leafless canes there are a few black leaves. They don't look just dead, but scarily black. As I mentioned, I've had this spirea for about 9 years. I've seen it in need of pruning and observed dead leaves, which usually turn brownish yellow and fall off. Not so with these leaves. Something's not right.
Any ideas out there?

I'm adding a detail of the above image which hopefully should spotlight the leaves.

I hack back my Spirea very aggressively in the late winter just to keep them in check and like so many plants they enjoy it very much. Much more dense and far less apt to flop as so many of my plants do.

It just kills me to look out at flopped over anything and I hate staking. From the Culver's Root to the Hydrangea and Goat's Beard everything seems to be flopping over this year.

Just venting Yellowbrick as your does not look like a pruning issue. Should you not get any activity out of it before winter cut it way back and see what happens. You also might be able to aggitate the roots with the fork and get sumpin going. Good Luck!!

Thank you all. I found this page
http://yardener.com/YardenersPlantHelper/LandscapePlantFiles/FilesAboutShrubs/ShrubFiles/Spirea/ProblemsofSpirea
and the problem described under "Shrub Stunted, Leaves Discolored by Root Knot Nematodes" seems to fit. I'm going to try their solution, if I can figure out what fish emulsion is and where to get it. My local nursery ought to be able to help.