One of my viburnums never woke up this spring, and part of another one look dead as well. After doing some searching, it appears as if there are borers. I think the one is completely dead...it was looking bad last summer, but I assumed it was just the hot weather and lack of rain in illinois. Is there any way I can save the one that is just starting to go? I'll have to cut down the dead one, but should I just cut down the other one too? I have 3 others that look good, lots of flowers and healthy leaves, no signs of borers that I can see. I there something I can put on the healthy ones to protect them?