We have a not sure of the spelling, rododamdra bush and half of it die

I can help with the spelling! It's rhododendron. Maybe this article will help: https://www.gardeningknowhow.com/ornamental/shrubs/rhododendron/rhododendron-care.htm

https://www.rhododendron.org/v48n2p85.htm

I know what you mean .I bought a plant myself did that .I cut the part that was dead off . The other part was okay . Good luck .

Brenda and 101onmax are right, on the part that appears dead, scrape to see if the inside is green, if it's deadwood cut it off. Trim little bits at a time until all the dead part is removed. It will be fine. The plant is still sending nutrients to the dead part, wasting tons of energy, so the quicker you get it off the faster it will start to heal

Be sure it is not planted near any Walnut trees’