Trees, Shrubs and Conifers: Spirea, 0 by Yellowbricks

Yellowbricks wrote:
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.