Larch tree disease found in Cumbria

Ramorum disease of larch trees has been found in Cumbria for the first time.

The disease, which kills larch trees very quickly and is a recent arrival in Britain, has been confirmed in two woods in the Eskdale Valley in western Cumbria.

Larch trees produce large quantities of the spores that spread the disease, which can infect many species of trees and plants. The only available disease control treatment is to fell the trees, preferably before the next spore release, which current knowledge indicates occurs in the autumn.

The outbreak is the second in North West England after one in southern Lancashire, and only the third outbreak in England outside the South West, where the disease has caused the premature felling of hundreds of thousands of larch trees.

There have been findings of ramorum disease on other plants, such as rhododendron, near the affected woods. Investigations are continuing into other suspected sites identified by aerial surveys in northern England, and the Forestry Commission believes there is a possibility that more outbreaks will be found.

Ramorum disease is caused by Phytophthora ramorum, a fungus-like pathogen that is particularly serious in Japanese larch trees and rhododendron, both of which produce large numbers of infective spores.

The outbreak was first suspected during aerial surveys to look for signs of the disease by the Forestry Commission, in conjunction with the Food & Environment Research Agency (Fera). These are continuing over large parts of Britain. Experts follow up with ground inspections and laboratory analysis of samples taken from trees showing possible symptoms of the disease. Other larch woodland in surrounding areas is inspected from the ground to check whether the disease is more widely present. Local woodland owners are being informed and given information about the disease and the measures for containing it.

Detailed information about P. ramorum, including a map of known outbreaks and a symptom recognition guide, is available from the Forestry Commissions website at www.forestry.gov.uk/pramorum.Follow tree pest and disease news at www.twitter.com/treepestnews

1. P. ramorum is a quarantine organism, and its presence on trees or woodland plants must be notified to the Forestry Commission, Fera or the Welsh or Scottish Government, which must take action to contain or eradicate it. Suspected cases of ramorum disease in larch trees can be reported to:
Scotland – ddas.nrs@forestry.gsi.gov.uk; tel. 0131 445 2176;England – plant_health_england@forestry.gsi.gov.uk; tel. 0117 372 1070;Wales – bww.ts@forestry.gsi.gov.uk; tel. 0300 068 0300.
A guide to symptoms is available from www.forestry.gov.uk/pramorum .

2. Both the affected properties in Cumbria are privately owned.

3. Key facts about woodland in Cumbria:Total woodland in county

• 67,600 hectares (ha)Woodland as a proportion of land area
• 9.9 per centTotal area of larch woodland in Cumbria
• 4,275 haLarch as a proportion of total woodland
• 6.3 per cent(To convert hectares to acres, multiply by 2.47.)

4.    P. ramorum can infect more than 150 species of plants and trees. It was first identified in the UK in a viburnum plant in 2002, and has since infected a wide range of plants here. In 2009 it was found in the environmentally important bilberry plant (Vaccinium myrtillus). The 2009 discovery of fatal infection in Japanese larches (Larix kaempferi) in South West England was the first time it had been found infecting a commercially important conifer tree species anywhere in the world.

5.    P. ramorum infection causes Japanese larch shoot tips to wilt and needles to turn black and fall prematurely. Cankers that bleed resin can appear on the branches and upper trunk. More than 2 million larch trees in the UK, mostly in South West England, South Wales and Northern Ireland, have been felled since 2009.6.    Larch is a durable, versatile timber that tolerates moisture and resists rotting when used in the ground. These qualities make it well suited for outdoor uses such as fence posts and panels, exterior wall cladding, boats, sheds and furniture, as well as indoor uses such as flooring and chipboard. It is easily stained, worked and finished. P. ramorum does not harm the timber, so logs from infected trees may enter the timber market, provided biosecurity measures are put in place to prevent accidental spread of the disease during timber movements.7.    There are about 134,000 hectares (331,000 acres) of larch woodland in Britain, equivalent to about 5 per cent of the total woodland area. Japanese larch is the most popular species with industry and end users because of its superior timber properties, but European larch (Larix decidua) and hybrid larch (Larix x eurolepis) are also grown in Britain.