Phytophthora Ramorum: Woodland at Risk

Yet again another tree disease has made the headlines. You might remember the article we wrote on the Ash Dieback Disease which gripped the nation earlier this year and devastated large numbers of trees across the UK, Poland and Europe.

Phytophthora Ramorum, also referred to as instant/sudden oak death has hit the headline as an outbreak reported in Wentwood Forest, near Newport has led to the felling of 500 acres of diseased trees.

To better understand the relatively new disease we asked The Forestry Commission’s Head of the Plant Health Services, Dr John Morgan for an overview of Phytophthora Ramorum and update on the current situation in Wentwood Forest:

What exactly is Phytophthora Ramorum?

“It is an organism similar to a fungus and belongs to the large Phytophthora* group of plant-damaging organisms. It is known to be able to infect more than 100 different species of plants, and is a distant relative of Phytophthora infestans, the organism which causes potato blight.*’ Phytophthora’ is Greek for ‘plant destroyer’”

How did it get to the UK?

“It most likely originated in Asia and entered, via Europe, in the international trade in live plants.”

How is it spread?

“It thrives in humid, damp conditions and can be spread by the wind and in watercourses, rain and mists especially, but also in soil, mud and plant material such as leaves and twigs attached to clothes, boots, vehicles, tools and animals.”

 

What are the symptoms and how do the public report cases?

“Symptoms on larch trees include: the trees only partially ‘flush’ with new growth in the spring; dieback (bare outer branches) and gingering of the foliage, which turns brown later in the season; cankers or lesions, often encrusted with resin in the bark of trunks and branches; and dead shoot tips turning black or grey in the autumn.”

“Most nursery findings have been on container-grown Rhododendron, Viburnum and Camellia plants, which can be badly affected by P. ramorum. Typical symptoms include blackening or browning and wilting of the leaves. Viburnum infection commonly occurs at the stem base, causing wilting and then death of plants.”

Suspected cases in trees and woodland can be reported:

in England to plant_health_england@forestry.gsi.gov.uk or 0117 372 1070; and in Scotland and Wales via our Tree Alert app or on-line reporting form at www.forestry.gov.uk/treealert.

What are the available treatments for the disease?

“The only available treatment is to fell or destroy infected, spore-producing* plants and trees such as larch and rhododendron, preferably before the next spore-producing season, to minimise the risk of infection spreading to more trees and plants.”

“(* Not all plants which can be infected by P. ramorum produce the spores which spread the disease. However, infected larch trees and rhododendron, which is often present in woodland, produce particularly large quantities of P. ramorum spores, which can be spread many hundreds of metres on the wind from tall larch trees.)”

What precautions can/are being taken?

“We survey high-risk areas of the UK from the air to identify possibly infected trees as early as possible. These are then inspected from the ground, and if Ramorum disease is confirmed we can issue a Plant Health Notice requiring the trees to be felled.”

“We also encourage, and in some cases require and enforce, ‘biosecurity’ measures. Some examples are:

  • cleaning forestry machinery before moving to new areas;
  • requiring that timber from infected woodlands is taken only to specially licensed sawmills or other wood users; and
  • provision of bike-washing facilities for mountain bikers to use before leaving infected woodlands.”

What actions are in place to stop trees like the ones in Wentwood Forest from being felled?

“The only treatment available to prevent the disease spreading and killing many thousands more trees is to fell infected trees and other susceptible trees close to them. Many owners are using this as an opportunity to replant their woodlands with a mixture of species to help make their woodland more resilient to future pest and disease attacks.”

More information about Phytophthora Ramorum is available from www.forestry.gov.uk/pramorum.

Resources

You can read more about the disease on the following resource:

http://genome.jgi.doe.gov/Phyra1_1/Phyra1_1.home.html

http://www.cabi.org/isc/?compid=5&dsid=40991&loadmodule=datasheet&page=481&site=144

http://www.bbc.co.uk/news/uk-scotland-south-scotland-24491061

http://www.itv.com/news/border/update/2013-09-26/plans-to-tackle-larch-disease-in-d-g/

http://www.hortweek.com/Arboriculture/article/1212128/Infected-Welsh-larch-replaced-native-species/

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