Origin of tree killer disease is still uncertain

I WISH to correct a number of erroneous statements attributed to Senator Paudie Coffey throughout the article headlined “Oak forests at risk from ‘killer tree fungus’ ” (August 25).

Senator Coffey states that the disease “arrived here in the rootstock of imported larch trees”. There is no evidence of this. It is not known for certain how the disease came to be established here, but given that it is a relatively new disease the findings so far have been mainly on mature Japanese larch trees and it is safe to discount the possibility of the disease arriving on the roots of imported Japanese larch plants.

Phytophthora ramorum can be spread by air dispersal and water, with airborne mists being a significant pathway.

As regards control measures for phytophthora ramorum, they have been in place here since 2002 when the EU introduced emergency measures under the EU plant health directive.

Following the findings on Japanese larch in Ireland, the forestry plant health contingency plan was immediately initiated and the EU technical guidelines on control measures followed. Aerial surveys of the region have been carried out and, to date, 42 forestry staff, including the department’s forestry inspectorate and Coillte staff, have been trained in the recognition of the disease and are carrying out surveys of larch forests.

In late 2009 the Forestry Commission in Britain confirmed an outbreak of the disease on mature Japanese larch in a forest in the southwest of England. Prior to this finding, phytophthora ramorum had never been found on Japanese larch, even in laboratory trials, and Japanese larch was not considered a host of the disease.

As a result of the finding, the Department of Agriculture, Fisheries and Food (DAFF) initiated a special precautionary survey to ascertain the presence or otherwise of the disease on Japanese larch in Ireland. The first positive finding was confirmed by the DAFF laboratory on July 13 this year. Since then the survey has been intensified and as well as the ground survey with department forestry inspectors and Coillte foresters, an aerial survey using civilian and Air Corps aircraft is being undertaken to help in the identification of diseased trees. All trees that have been tested positive for the disease have been felled. Detailed information for forest users is available on both the department’s website and the Coillte Outdoors website. Signs outlining the hygiene measures are posted at the entrances to known infected forests. Water and scrubbing brushes have been placed at the entrances to known infected forest sites for use by the public.

Phytophthora ramorum is also known as Sudden Oak Death. This name originated in the USA where the disease has caused extensive damage to a number of tree species, in particular tanoak, along the Californian coast.

However, the name is somewhat of a misnomer in the European context as there hasn’t been sudden death of oak trees here and, to date, there have been no findings of this disease on the two species of native oak in Ireland, which appear to be far more resistant to the disease.

Martina Kearney

Press Officer

Department of Agriculture, Fisheries and Food

Kidldare Street

Dublin 2