I was talking to someone last week who knows a lot about gardening and owns a tissue-culture propagation business. He told me that many of the Emerald Cedar and Pyramidalis Cedar hedges we see dying the past few years are not necessarily succumbing to drought but are, in fact, dying from root rot -namely Rhizoctonia and that this fungal disease can be or is spread through the foliage. I've been trying to find corroberation on the web but not getting very far . . . can any of you experts say if this is correct information? First, is Rhizoctonia a likely cause of 'cedar' hedges dying and second, can it be spread through the leaves? Note: I'm asking specifically about the recent, widespread death of Thuja plicata as well as arborvitae hedges on the east coast of Vancouver Island.
I have had death of one or two young plants which I attributed to normal survival percentage (let’s say 2 out of 30) I assumed they were not as happily establishing new roots etc because they were planted in May after septic system total renovation - i thought maybe their somewhat bare roots stayed in sun longer before the rough contractor people planted them ... we then had soaker hose on them This was approx 2010 I think. ———— Do you have any PHOTOS of the issue you suspect on East Vanc Island? Is it the entire row (as in hedge) or just a few in the hedge line up? Pictures would be interesting to view . If this disease is here - wow, those hedge cedars are everywhere - how to control disease spread and sterilize soil where dead installations have been removed and how to dispose of the dead ones etc. Would this spread to native trees I wonder ? I have heard of issues replanting Okanagan apple orchard trees due to soil disease - I suppose there would be academic papers on that study circa 1990’s I think at Summerland BC Ag Canada research station. I hope this link works - I think this was the study and maybe there have been updates since An Error Occurred Setting Your User Cookie
Diseases arborvitaes get in our region are shown and described on these pages from Oregon State University: Host and Disease Descriptions
Ron - thank you for suggesting where I read that, Thuja occidentalis 'Smaragd' is very susceptible to Phytophthora so perhaps it is also quite susceptible to Rhizoctonia. I was questioning whether a root pathogen can be introduced through the leaves until I read on another site that, "Leaves that come in contact with the soil can become infested with Rhizoctonia, causing aerial blight. Aerial blight can spread quickly if the leaves are wet, plants are too close together and/or the humidity is high ...". Rhizoctonia Root Rot: Symptoms And How To Control | PRO-MIX Greenhouse Growing So now I wonder if it would be a good practice to remove the lowest branches of Arborvitae hedges or if a wood chip mulch would provide enough protection. I do not have any photos at the moment but share Georgia Strait's concern that this disease maybe becoming more prevelant.
