RHS Names Top Garden Diseases for 2012

Tuesday 5 March 2013

Scientists gain valuable insights from members’ enquiries

The Royal Horticultural Society (RHS) has announced the top garden diseases of 2012 based on enquiries received by the charity’s Members' Advisory Service. As in 2011 ever-prolific honey fungus topped the list after its presence was confirmed on 188 samples covering 58 plant genera. Pythiums and leaf spots again occupied the second and third positions with rusts and phytophthora diseases completing the top five.

But while there were few surprises at the top of the list the most significant development during 2012 was the massive increase in the number of cases of Cylindrocladium box blight. The reported cases of box blight caused by Cylindrocladium buxicola hit a 10-year high of 100, which is more than double the 2011 figure. The increase means the disease has climbed four places up the list from 9th in 2011 to 6th in 2012.

Box blight is a fungal disease of box resulting in bare patches and dieback of box, especially in topiary and parterres. The fungi survive on fallen leaves and produce spores when conditions are suitable. These spores are dispersed in water where there is high humidity, spreading and infecting over short distances by water splash. High rainfall during the growing season makes plants particularly vulnerable as young leaves are more susceptible to infection.

Other diseases that took advantage of a very wet 2012 were Pythium root rots, fungal leaf spots and scabs – which returned to the top 10 after a 12-month absence.

Dr BĂ©atrice Henricot, RHS Principal Research Scientist, Plant Pathology said: “Through our daily interaction with RHS members via our advisory and diagnostic services, we obtain invaluable information about the health of gardens across the country. The annual top-15 list helps gardeners learn more about those diseases that are causing them concern, and the most effective ways to combat them.

“Although the 2012 list is very similar to previous years, the high rainfall levels we experienced from late April provided the perfect breeding ground for some diseases to thrive, most notably Cylindrocladium box blight.
“The impact of climate change, which could mean wetter, warmer winters, could result in an increase in these types of disease. While there is currently no cure for box blight, RHS scientists continue to work to develop measures that can be taken to manage the disease.”



Notes to editors

For more information, please contact Garfield Myrie in the RHS Press Office on 020 7821 3060 or email garfieldmyrie@rhs.org.uk

Photographs are available to download at www.picselect.com (register online free of charge).

Top 15 diseases in 2011 and 2012
(number of enquiries to the RHS Members' Advisory Service in brackets).














Facts about honey fungus
Honey fungus is the common name of several species of fungi within the genus Armillaria. Honey fungus spreads underground, attacking and killing the roots of perennial plants and then decaying the dead wood. It is the most destructive fungal disease in UK gardens.
There are no chemicals available for control of honey fungus. If honey fungus is confirmed, the only effective remedy is to excavate and destroy, by burning or landfill, all of the infected root and stump material. This will destroy the food base on which the rhizomorphs feed, and they are unable to grow in the soil when detached from infected material.

To prevent honey fungus spreading to unaffected areas, a physical barrier such as a 45cm (18in) deep vertical strip of butyl rubber (pond lining) or heavy-duty plastic sheet buried in the soil will block the rhizomorphs. It should protrude 2–3cm (about 1in) above soil level. Regular deep cultivation will also break up rhizomorphs and limit spread.

About the RHS
The Royal Horticultural Society was founded in 1804 by Sir Joseph Banks and John Wedgwood for the encouragement and improvement of the science, art and practice of horticulture. We held our first flower shows in 1820, were granted a Royal Charter in 1861 and acquired RHS Garden Wisley, the first of our gardens, in 1903. From our first meetings in a small room off London’s Piccadilly, we have grown to become the world’s largest gardening charity.

Today the RHS is committed to providing a voice for all gardeners. We are driven by a simple love of plants and a belief that gardeners make the world a better place. 200 years on we continue to safeguard and advance the science, art and practice of horticulture, creating displays that inspire people to garden. In all aspects of our work we help gardeners develop by sharing our knowledge of plants, gardens and the environment.

RHS membership is for anyone with an interest in gardening. Support the RHS and secure a healthy future for gardening. For more information call: 0845 130 4646, or visit www.rhs.org.uk/join

RHS Registered Charity No. 222879/SC038262


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About the RHS

The RHS believes that gardening improves the quality of life and that everyone should have access to great garden experiences. As a charity we help to bring gardening into people's lives and support gardeners of all levels and abilities; whether they are expert horticulturists or children who are planting seeds for the very first time.

RHS membership is for anyone with an interest in gardening. Support the RHS and secure a healthy future for gardening. For more information call: 0845 130 4646, or visit www.rhs.org.uk

RHS Registered Charity No. 222879/SC038262