Rhododendron Problems
This spring (or is it still winter) I have started to get quite a few calls about Rhododendron showing root rot symptoms. There seems to be a pattern in the symptoms but so far I can't see a pattern as to the age of the plants, planting site, length of time planted or species/cultivar. Would like to hear from others in the industry to see if there's something we're missing. Meanwhile, I would recommend pruning out branches that are obviously dead and follow a wait and see approach to the rest. By May we should be able to see if the plants are going to rebound. Based on what I have seen or heard about I suspect that this issue is weather related; lots of rainfall followed by a colder than normal winter. Commercial applicators could consider an application of Subdue as a drench to suppress any of the root rot pathogens. This product is a restricted use fungicide and can be an expensive option.
For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.
