Thurles Information

Phytophthora Ramorum or Sudden Oak Death

IRELAND’S trees could soon be under serious attack from a recently identified deadly disease, which experts have warned, poses a huge threat to Irish biodiversity and could spell disaster for the country’s few remaining native forests.

The Department of Agriculture confirmed this week that it was investigating an outbreak of the fungal disease phytophthora ramorum, (Common Name – Sudden Oak Death) which so far has affected only a small number of Japanese larch trees, Beech trees and Noble Fir trees in the Tipperary/Waterford region.
The department further confirmed that the disease had also been found in Northern Ireland and it was liaising closely with the North’s Department of Agriculture and Rural Development. The Japanese larch variety represent 3% of the total tree population in Ireland and it is believed that the disease may have spread from the US, where it killed millions of trees, travelling first to Britain and then into Ireland.

The outbreak of this fungus, which is related to the potato blight, Phytophthora infestans , could pose a particular threat to the 1% of Ireland’s remaining precious oak forests if Irish oaks proved susceptible to the strain. It would also have a disastrous effect on plantations of single tree species and eventually effect on the insects and birds life that these trees support. Tourism could also be effected with scenic areas being prohibited to visitors as part of controls.

Phytophthora Ramorum was first discovered in California in 1995 when large numbers of Tanoaks died mysteriously. This disease which can be transmitted by wind and rainwater, also infects a great number of other plant species, significantly rhododendrons, causing a non-fatal foliage disease commonly known as ‘ramorum dieback’.

The disease is a fungus-like organism and its spores enjoy 100% survival rates at temperatures of 0°C and 20°C.  The first recognisable symptom is a burgundy red or thick black sap liquid, bleeding from cankers on the tree’s bark surface. The disease trives in cool, wet climates.

Just one of the major mechanisms of dispersal for this fungus, is rainwater splashing its spores onto other susceptible plants and into watercourses. Over use of man made drainage schemes, which must take responsibility for a great deal of recent flooding in Ireland, can insure spores can be carried for great distances. Hikers, mountain bikes, those involved in equestrian persuits and people engaged in other various outdoor activities, may also unwittingly move the pathogen into unaffected areas. In most cases, cleanliness practices involve the cleaning of all potentially infested surfaces of all foliage and mud, before leaving an infested area, e.g. shoes, transport vehicles and animals, etc.

Interesting to note that phytophthora ramorum (Phytophthora comes from the Greek word phytón, meaning ‘plant’ ), the relative of phytophthora infestans or Potato Blight, was one of more than seventeen agents researched by the United States as potential biological weapons, before it suspended its biological weapons program, latter completed in 1973.