this yellow growth is near the bottom with healthy looking leaves on those stems as it grows. I am concerned that the leaf hoppers etc. will spread disease to my other clematis. Should I destroy it? The plant is probably "Regency" but may be "Pink Champagne". It dies completely to the ground each winter. Thanks!!

I'm not sure I would automatically assume it's a virus. Since it appears to be showing on only the lowest, oldest foliage so far, it could just as easily be a nutrient deficiency. Lack of adequate magnesium can also produce similar appearance. I'd remove the affected leaves and give it a dose of Epsom salts and see what happens before I dug it up.