New sudden oak death introduction appears in UK

British forestry scientists have identified a fourth genetically distinct lineage of Phytophthora ramorum (the pathogen known to cause sudden oak death). In the UK, including Northern Ireland and many western parts of Great Britain (especially southwest and northwest England, south Wales, and southwest Scotland), P. ramorum is causing dramatic mortality in Japanese larch trees.

The increasing intensity of the P. ramorum outbreaks in the UK led researchers to analyze samples from the new findings further, which resulted in the discovery of a fourth, genetically distinct lineage of the pathogen.
Clive Brasier, an emeritus professor with the Forestry Commission's Forest Research agency, said he believed that the previously unknown European Type 2 (EU2) lineage had been recently introduced into southwest Scotland and Northern Ireland, based on genetic analysis.

"We are still uncertain about the pathway by which the new lineage has arrived in the UK, and we are still trying to assess the extent of its distribution," Professor Brasier said. "We have tremendous biosecurity concerns, including this new form of P. ramorum. Over the past year alone in the UK we have discovered chestnut blight, Asian longhorn beetle, Chalara dieback of ash, and several other invasive forest pests."

Despite its common name in North America, the UK's native oak species (Quercus robur and Q. petraea) have been little affected by P. ramorum. However, it has proved particularly destructive to Japanese larch (Larix kaempferi) in the UK since it was first found to be the cause of significant mortality in this species in England in 2009. Larch trees also produce huge numbers of infective P. ramorum spores, which spread into the local environment through wind and rain events. To date, more than 3 million larch trees have been compulsorily felled in the UK in an effort to bring the disease under control.

For more: www.suddenoakdeath.org.