Globe caragana - 1/2 of plant dead foliage?

I have a globe caragana that has 1/2 of it's foliage has died off: (here's a picture): .
1) Should I trim of the dead foliage (wood and all) or should I see if it will grow new leaves next year? 2) What cause this? A fungus? Grasshoppers are very numerous...

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