My 20 year old Thuja excelsa hedge has been diagnosed (BC Ministry of Agriculture Lab) with two foliar blights. Keithia blight associated with Didymascella thujina and Coryneum blight caused by Seiridium cardinale. The hedge is about 12 feet high, 13 ft. wide, and approximately 36 ft. long and has 8 trees planted on 4 foot centres. What shall I do? One, try to treat these fungi? What to treat these fungi with and where to purchase the fungicide. or Two, rip out my hedge and replant? I would hate to have to do this.
Didymascella thujina is treatable with fungicides, but Seiridium cardinale isn't. However, Seiridium cardinale is very unusual on Thuja plicata (Thuja is more resistant to the canker than many other cypresses), so the plants may not get badly affected by it and might outgrow it.
I do thank you for your input. I have started to investigate which fungicides might be applicable in dealing with these fungi. So far, it looks as though the treatment might involve multiple applications of (hazardous to my health) chemicals that require very careful handling and in the end, promise of only potential 'control', not eradication. The thought of exposing myself to this possible 'never ending process' is daunting.