Need help please with disease on Rhododendron
dottyw
Posts: 16
Our recently purchased property in Ontario, Canada came with 8 rhododendrons in poor shape, although most are blooming right now. All bushes have brown spots and / or perfectly round white spots the size of a pin head on one or both sides of leaves, damaged or rolled up browning leaves or fallen off dried up leaves, crust on branches. Some limbs look dead, many have leaves and flowers at the top only and have no leaves below. Will this stay, or can I expect new growth where there is baldness now? Underneath several plants is this strange little round fungal type growth in the soil, see in the picture with the label. Several are Rhododendron English Roseum, one as Niering Rhododendron. A nursery lady said its a common fungal disease and sold me a spray bottle of Safer's Defender Garden Fungicide. I am planning to repeat as recommended. But.... should the branches not also be sprayed?? And would the ground not be contaminated and need treatment ? And should I not be dealing with those little round things growing in the soil ? How? What are they? The lady in the nursery ignored this question. I cannot get the Safer's concentrate solution here, its discontinued. Is there another suitable product that would come in concentrated form ? I'd very much would love to save what I can. Looking forward to your input .
0
Posts
I'm by no means sure, but it's a possibility.
It may be that your plants have a combination of problems. Once they are weakened it leaves the plant open to other diseases.
Your plants do look very poorly.
Sometimes these infections get a hold if the plant has been stressed. A lack of water being one of the most common causes.
Rhododendrons need an acidic to neutral soil to thrive in and will struggle if the soil is alkaline.
If the spray you have is a systemic fungicide then it will be absorbed by the leaves and then travel through the entire plant - so no need to spray branches. It should say on the label if it is systemic.
I've no idea what the little fungi may be - but most are very beneficial.
In terms of pruning Rhodos they can be pruned back as hard as you like.
Mine was about 12ft across and 10ft tall - I reduced it all to about 2ft and it is sprouting strongly all over.
But mine was healthy to start with.
Wisdom is not putting it in a fruit salad.
What time of year was it when you did that big pruning job?
I've got one I want to try and rejuvenate after it has flowered this year .... or would autumn be better?
Thanks,
Bee x
A single bee creates just one twelfth of a teaspoon of honey in her lifetime
Autumn would probably be best, but they're such tough plants anytime is fine.
I guess if you do it now, you may get flowers next year. I got none this year.
The density and rate of the new growth is impressive - a bit too impressive for my liking tbh
Wisdom is not putting it in a fruit salad.
It's never too hot or dry here, so it might put a spurt on before it gets too cold.
Bee x
A single bee creates just one twelfth of a teaspoon of honey in her lifetime
I can't see any new growth at all on your rhododendrons. I don't think you need fungicide - water is the main requirement, and I'd guess the folk you bought your house from, haven't been regular with the watering. Rhododendrons like moist, leafy soil and shade or part shade. They are plants of woodland or woodland edges. As @Pete.8 says, they won't thrive in alkaline soil. Do you know what the soil is like under that mulch?
If they recover, they may well shoot away from the base, in which case you can trim off the old crabby bits.
Mine have sprouted new shoots over a foot long already this year.
Wisdom is not putting it in a fruit salad.
If they're recently planted, they probably haven't been watered well enough. If they've been there a long time, there's something very wrong with the site/soil. Alkaline soil really doesn't suit the majority of them. It may also be that they've not had the planting holes prepped well, or they may have been pot bound, which can prevent good outward growth of the root system. They need lots of water as they're shallow rooted.
Were they there when you viewed the house? Sometimes people plonk stuff in to make a garden look more appealing, but they don't give them the care.
@Bee witched - you can really prune them at any time here. After flowering is always a good time.
I live in west central Scotland - not where that photo is...
Bee x
A single bee creates just one twelfth of a teaspoon of honey in her lifetime