Ramorum disease, which has caused the early felling of about 2 million Japanese larch trees in the UK, has now been found infecting the European larch species for the first time.
Scientists from the Forestry Commission’s research agency have confirmed infection by the pathogen Phytophthora ramorum in a European larch (Larix decidua) in woodland near Lostwithiel in Cornwall, south-west England, in an area with infected Japanese larch trees nearby.
Ben Jones, the Forestry Commission’s Phytophthora operations manager, said,
"Although it is bad news that this lethal pathogen has proved able to infect yet another tree species, it was not entirely unexpected, given the physiological similarities between European and Japanese larch."
Britain’s woodland owners and managers have been on high alert since P. ramorum was first found infecting and killing thousands of Japanese larch (Larix kaempferi) trees in south-west England in 2009, and Mr Jones added,
"It is too soon to know how susceptible European larch is to P. ramorum infection, or whether it will be a sporulating host, that is, whether it will produce the spores that spread the pathogen; and if it is, how heavily it will sporulate.
"However, in light of this development we are urging woodland managers once again to be diligent about inspecting their trees regularly for signs of disease and decline, and to report any suspicious symptoms to us.
"We will be resuming aerial surveys soon, after the trees have flushed with new needles, to look for larch woodlands with symptoms of dieback, and following up with ground inspections to identify the cause of the symptoms."
The symptoms of P. ramorum infection in larch include excessive resin bleeding, sunken or cankered areas of bark, wilting of the needles with the tree canopy turning grey, and branch and shoot dieback with a distinctive ginger colour.
• The Forestry Commission has published a comprehensive update report on the outbreak of P. ramorum on larch, which is available from a link at www.forestry.gov.uk/pramorum. And two grant aid packages for helping the owners of infected larch trees have been extended until March 2012 - details are available from the same pages.
