I wonder if anyone knows what my rhodo is suffering from. It is about 20 years old. It is just about to bloom and many of the leaves look like this and then they fall off. I don't remember the dying leaves looking like this before. The rhodo has been fertilized with rhodo fertilizer sparingly in April. What should I be doing to remedy this?
It's either powdery mildew of rhododendron or lace bugs. If the former there will be a moldy looking growth visible on the blotched portions of the leaf undersides, if the latter (and the insects are still present) those can be seen on the affected areas also.
Thanks, Ron. I am looking at the leaves with a magnifying glass and I can't see mildew and nothing comes off if I rub them. I don't see any bugs on the rhodo but I will look into that.
Definitely not lace bugs. How old are the leaves that are falling off? Are they dying earlier than in previous years or simply looking worse before doing so?
The leaves are here and there, many are just a single leaf near the flower bud. I think they are dying earlier and also looking worse. Lily of the Valley have taken over under the rhodo. I wonder if this might be bad?
From the rhododendron's point of view, I'm sure it would be happier without having to share available resources such as water and nutrients with lily-of-the-valley but, according to some people, they can co-exist successfully. I would consider getting rid of it but that would be a big challenge unless you were prepared to use a weed killer like glyphosate. Besides the possibility of powdery mildew is downy mildew which can also be a problem with rhodos growing in compromised situations like yours. I found an article about mildew in an old American Rhododendron Society journal which may be of some help. The description of downy mildew on leaves sounds more similar to how yours look but of course it's impossible to say for sure from a photograph. Here is an excerpt but you'd need to read the whole article for a thorough explanation of how to deal with both powdery and downy mildew. "Downy mildew is indicated by yellowish patches on the surface of affected leaves, and on the under surface of the leaves it will appear as a whitish gray or even a bluish-gray mealy growth - symptoms similar to those of rust. The only true way to determine the source of the disease is with a magnifying glass or by consulting a pathologist." https://www.rhododendron.org/v48n1p19.htm#:~:text=Downy mildew is indicated by,similar to those of rust.
Thanks for your help, Margot. I have looked at the leaves with a magnifying glass and I do not see or feel anything growing on them. I was thinking of digging out the lily of the valley but I was worried about damaging the roots of the rhodo. If I don't dig them out would a bit more rhodo fertilizer be good?
Can you take a « context » photo of overall shrub and post I wonder if last few summers of intense heat one week then no rain etc have stressed your Whitney - making it susceptible to opportunists It’s such a reliable old rhodo
'Anna Rose Whitney' is one of those quite prone to what I'd always assumed to be mildew until I encountered one instance where a nursery was being sprayed for lace bugs, saw a general similarity of damage with long established specimens being spoiled since mildew cropped up in our region during the 1990's. With many mistakenly thinking that the premature leaf drop and resulting thin appearance they were seeing with various rhododendrons after the killer winter of 1990 was cold damage.
Today, I carefully took out most of the lily of the valley under the rhodo. I watered deeply and put on a small amount of fertilizer. I picked off and discarded bad-looking leaves. If it is not sunny tomorrow I will spray the leaves with apple cider vinegar diluted in water. I don't suppose there is any harm in doing this. I will hope for the best. Does anyone know if Safer's Fungicide Spray would be a better bet than apple cider vinegar. I might just have enough time to spray before the blooms open. I really appreciate all the information I have received on this forum.
I don't have a camera right now to take a picture. I have been good about watering but still the heat is no good. My other rhodos are all doing well. I would hate for something bad to spread to the other rhodos.
Remember to go to bottom of post and upload photo of overall context - the big picture How do your other rhodos look? What is next to your Anna Rose Whitney? And how is that doing? ÉDIT - oh I think we just crossed internet paths
Hello @Irish - I understand it's hard to send a photo when you don't have a camera. :-) I agree with @Georgia Strait though that it is important for us to see a few shots of the whole plant as well as a few close-ups before venturing any more opinions or offering advice. PS I just saw the message you sent at 6:25pm and think you are on the right track. I can't say if Safer's Fungicide Spray would be a better bet than apple cider vinegar but personally, I'd choose the Safer's product because I think it would be more likely to help. Please keep us posted about how your rhodo thrives over the summer.
