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RHS disease ranking highlights top 10 gardening problems in 2023

The Royal Horticultural Society (RHS) has published its annual disease ranking, revealing the top ten problems for gardeners in 2023.

Damp conditions in spring and summer were the driving influence in the prevalence of certain diseases, with the following four new entrants to the top ten list: blossom wilt of fruit trees, pocket plum, tulip fire and slime flux. Fruit trees continued to be under threat from disease, with apples, pears, and Prunus among the top five hosts and collectively resulting in over 1,000 enquiries to the RHS advisory service, a 50% increase on the previous year.

The top diseases for 2023 are:

  1. Honey fungus
  2. Apple and pear scab
  3. Rose black spot
  4. Pear rust
  5. = Blossom wilt of fruit trees
  6. = Bacterial leaf spot and canker of Prunus
  7. Phytophthora root rots
  8. Pocket plum – Taphrina pruni
  9. Tulip fire
  10. Slime flux

Wet weather last spring provided perfect conditions for tulip fire – which produces brown spots and twisted, withered leaves - to take hold, seeing the disease make a return to the top 10 for the first time in several years. The damp spring conditions are also likely to blame for high cases of pocket plum, which causes elongated, hollow fruits with no stone on plums and damsons, as well as some ornamental Prunus, rendering the fruit inedible.

Slime flux, which affects a wide range of trees and shrubs, was another new entrant to the list. It is thought that the bacteria colonises trees via their roots, so the increase in cases may be a result of the wet winter in 2022/ 2023 and associated waterlogged soils.  In addition, there was a rise in reports of rose black spot and pear rust, which can both likely be attributed to the warm and wet weather conditions during the summer.

Honey fungus topped the list for the 28th year running, having held the top spot since the list was first published in 1995. The fungus has a large host range of more than 140 garden plants, with the most common hosts in 2023 being privet, rose and viburnum, and results in dramatic symptoms, including death, cracked and bleeding bark and failure to flower.

To minimise plant disease this year gardeners are advised to apply mulch to improve drainage, while ground that has been laid sodden should be lightly pricked with a fork and spread with an organic mulch such as well-rotted manure, so plants grow with improved health and disease is less likely. Now is also a good time to prune out any diseased and damaged material before it can spread spores when the temperature is warmer. 

Liz Beal, RHS Plant Pathologist, said: “Unusually wet weather in 2023 had a significant effect on plant health across the UK, with the prevalence of tulip fire and pocket plum demonstrating the impact of prolonged damp conditions. Following the extreme drought of the previous year, many gardeners are left wondering how to prepare for unpredictable weather patterns. Understanding the conditions of your garden is key in deciding which plants will thrive where; the right plant in the right place will always have a better chance of fighting off infection. Additionally, gardeners can help combat many of the most common diseases in our ranking by practising good hygiene, keeping tools clean and removing – and safely disposing of - diseased plant material from their gardens.” 

The RHS Plant Health team uses the disease ranking to inform their research and advice. Current research at RHS Wisley’s Hilltop: Home of Gardening Science includes investigating the effective management of Phytophthora in gardens, examination of different methods for managing rose black spot and characterising the dispersal mechanisms and variation of honey fungus populations.

RHS members get free access to the charity’s Gardening Advice Service, available by phone or email. Find out more about becoming a member at: www.rhs.org.uk/join

RHS advice pages are available for everyone, for further information, visit: www.rhs.org.uk/advice

– ENDS –

Notes to editors

Notes to Editors:

For further information, images or interviews, contact Gina Miller [email protected] or the RHS Press Office at [email protected] / 0207 821 3080.

For more information visit: https://www.rhs.org.uk/science/articles/2023-diseases

Top enquiries to the Pathology section of RHS gardening advice 2023, 2022 and 2021

 

Top diseases 2023

 

 

Top diseases 2022

 

Top diseases 2021

1

Honey fungus

=

1

Honey fungus

1

Honey fungus

2

Apple and pear scab

^

2

Phytophthora root rots

2

Pear rust

3

Rose black spot

^

3

Powdery mildew of Prunus

3

Bacterial leaf spot and canker of Prunus

4

Pear rust

^

4

Rose black spot

4

Tomato/potato late blight

5=

Blossom wilt of fruit trees

^

5

Peach leaf curl

5

Rose black spot

5=

Bacterial leaf spot and canker of Prunus

^

6

Brown rot of fruit

6

Bracket fungi

7

Phytophthora root rots

˅

 

7

Silver leaf

7

Powdery mildew of Prunus

8

Pocket plum- Taphrina pruni

^

8

Apple and pear scab

8

Brown rot of fruit

9

Tulip Fire

^

9=

Pear rust

9

Phytophthora root rots

10

Slime flux

^

9=

Apple and pear canker

10

Box blight

 

 

 

9=

Bacterial leaf spot and canker of Prunus

 

 

 

 

 

 

 

 

 

 














About the RHS

Since our formation in 1804, the RHS has grown into the UK’s leading gardening charity, touching the lives of millions of people. Perhaps the secret to our longevity is that we’ve never stood still. In the last decade alone we’ve taken on the largest hands-on project the RHS has ever tackled by opening the new RHS Garden Bridgewater in Salford, Greater Manchester, and invested in the science that underpins all our work by building RHS Hilltop – The Home of Gardening Science.

We have committed to being net positive for nature and people by 2030. We are also committed to being truly inclusive and to reflect all the communities of the UK.

Across our five RHS gardens we welcome more than three million visitors each year to enjoy over 34,000 different cultivated plants. Events such as the world famous RHS Chelsea Flower Show, other national shows, our schools and community work, and partnerships such as Britain in Bloom, all spread the shared joy of gardening to wide-reaching audiences.

Throughout it all we’ve held true to our charitable core – to encourage and improve the science, art and practice of horticulture –to share the love of gardening and the positive benefits it brings.

For more information visit www.rhs.org.uk.

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The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.