Oyster-shaped growths on branches and trunk of lilac bush
Numerous oyster-shaped growths appeared suddenly on my lilac bush in November, after 2 months of heavy rain. They are covering multiple large branches, as well as areas of the trunk, and are grey and white in color with striations on the edges. They look exactly like oyster shells. My lilac bush is now leafing out, and has many blossom buds, so it does not appear to be harmed. Are these fungi from such a wet Winter? How do I treat them, other than to remove most of the branches down to the trunk of the bush? Thanks!
Polk County Oregon fungus
This is a species of Trametes. If it is hairy, it is Trametes hirsuta, otherwise it is Trametes versicolor. Trametes versicolor is a known pathogen of Lilacs, and it rots the lignin in the wood. Check with your extension agent to see if there are known treatments, but it is likely you will have to drastically cut them back to sound wood. The bulk of the fungus is inside the branches, and the shelfs that you see produce spores. The wet winter may have helped them grow, but the spores were brought in by the wind or insects.
Thank you for your helpful information. Do you know of anything I can do to protect my other unaffected lilacs?
I don't. You should contact a nursery or extension dept. Good luck!