Phytophthora ramorum is reported to have been found in European larch, following a discovery by Forestry Commission scientists in woodland near Lostwithiel in Cornwall.
The disease has already resulted in the felling of around two-million Japanese larch trees, and the latest finding was in woodland close to infected Japanese larch.
Forestry Commission Phytophthora operations manager Ben Jones said: "Newly-arrived pathogens that infect a range of tree species are a growing threat in Britain, and all of us in the forestry sector must embed constant vigilance into our woodland management as a part of our response to it."
He said it was too soon to tell whether European larch would be a sporulating host for P. ramorum and said the commission would carry out aerial surveys of the area this spring and summer.
"P. ramorum prefers a moist environment, so we would expect European larch on the wetter, western side of Great Britain to be the most vulnerable," he added. "However, we are urging tree owners in all areas to be diligent about inspecting their trees."
FOREST RESEARCH TESTS LOOKING AT SUSCEPTIBILITY TO DISEASE
In 2010, Forest Research tested Japanese larch, European larch and hybrid larch against susceptible hosts such as rhododendron and Vaccinium for foliage susceptibility and ability to sporulate P. ramorum.
Forest Research principal pathologist Joan Webber said: "What we have come to realise from our work over the past 18 months is that the foliage, or specifically the needles, of larch probably only become susceptible to infection by P. ramorum as winter approaches, and if infected at this time they support abundant sporulation.
"It seems to be the nature of larch to carry the source of its susceptibility and sporulation potential.
"In comparison, the needles of other conifers seem to support little or no sporulation and are usually not very susceptible to infection."