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Photinia black spot problem & treatments?

#1 · 27th February 2024, 2:18 pm

Hi Lee

I have a problem with my Photinia "Red Robin". It has been living happily in a pot and growing (slowly). I noticed recently that it's leaves are covered in brown marks/spots and wondered what this means? Someone said to me that I should pick off the infected leaves, but if I do that, there'll be no plant left! I'm reluctant to do that anyway, because as you will see from my pics, new growth is beginning to appear.

I put a cane in to support it last summer, as it was flopping about, but I'm now left with a straggly stem and it's not bushing out like I'd hoped. Is it something that can be cured, as I don't want any new leaves to become infected? Thank you as always for your advice.

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#2 · 29th February 2024, 8:59 am

Quote from Lee Garden Ninja on 29th February 2024, 8:59 am
Hi @my-tiny-garden
Good to hear from you again! It sounds like you're moving on with your garden rework, which is great to hear.
Ok, black spot on a Photinia means one thing. Photinia black spot - a fungal disease. But don't panic; 99% of the Photinia I see get affected by this at some point; mine at home has it as well.
What is Photinia Black Spot?
Photinia black spot is a fungal disease that affects Photinia plants, particularly Photinia × fraseri and Photinia serratifolia. It manifests as dark, circular spots on the leaves, often surrounded by yellow halos. As the disease progresses, the spots may coalesce, leading to extensive leaf damage and defoliation. Photinia black spot is caused by the fungal pathogen Diplocarpon mespili.
Black spots won't kill your plants but are unsightly and weaken their vigour, so it's always prudent to take some steps to reduce them.
How to Treat Photinia Blackspot
For the most part, removal of the leaves is the best bet in severe infestations, though yours looks quite light in infection. If it gets worse, definitely remove the leaves and bin them, don't compost them as they spread. The new leaves will take over.
Pruning
Pruning can also help remove very heavy infestations. Prune affected branches and foliage to remove infected plant material. Dispose of pruned material away from the garden to prevent the spread of fungal spores.
Improve Air Circulation
Ensure adequate spacing between plants to promote air circulation and reduce humidity levels, which can contribute to fungal growth. Trim nearby vegetation to allow light and air to penetrate the canopy. Usually, Photinias or Red R0bins in shady spots with little air flow suffer the worst, especially when placed under tree canopies where water drops onto them as well. So move yours somewhere sunny for this year.
Mulching to Remove Black Spot
Giving your container-grown red robins or ground-planted shrubs a good mulch each spring can really help boost their resilience to black spots. The same goes for Roses, too. It just helps keep them as resilent as possible to the fungus and black spots.
I hope that helps!
Lee Garden Ninja

Hi @my-tiny-garden

Good to hear from you again! It sounds like you're moving on with your garden rework, which is great to hear.

Ok, black spot on a Photinia means one thing. Photinia black spot - a fungal disease. But don't panic; 99% of the Photinia I see get affected by this at some point; mine at home has it as well.

What is Photinia Black Spot?

Photinia black spot is a fungal disease that affects Photinia plants, particularly Photinia × fraseri and Photinia serratifolia. It manifests as dark, circular spots on the leaves, often surrounded by yellow halos. As the disease progresses, the spots may coalesce, leading to extensive leaf damage and defoliation. Photinia black spot is caused by the fungal pathogen Diplocarpon mespili.

Black spots won't kill your plants but are unsightly and weaken their vigour, so it's always prudent to take some steps to reduce them.

How to Treat Photinia Blackspot

For the most part, removal of the leaves is the best bet in severe infestations, though yours looks quite light in infection. If it gets worse, definitely remove the leaves and bin them, don't compost them as they spread. The new leaves will take over.

Pruning

Pruning can also help remove very heavy infestations. Prune affected branches and foliage to remove infected plant material. Dispose of pruned material away from the garden to prevent the spread of fungal spores.

Improve Air Circulation

Ensure adequate spacing between plants to promote air circulation and reduce humidity levels, which can contribute to fungal growth. Trim nearby vegetation to allow light and air to penetrate the canopy. Usually, Photinias or Red R0bins in shady spots with little air flow suffer the worst, especially when placed under tree canopies where water drops onto them as well. So move yours somewhere sunny for this year.

Mulching to Remove Black Spot

Giving your container-grown red robins or ground-planted shrubs a good mulch each spring can really help boost their resilience to black spots. The same goes for Roses, too. It just helps keep them as resilent as possible to the fungus and black spots.

I hope that helps!

Lee Garden Ninja