The source of the ash dieback disease has been traced back to Asia by scientists in Norwich.
There are concerns that if one more type of spore arrives in our woodlands it could mean the end of the species as we know it.
Click below to watch a report by ITV News Anglia's Kate Prout
Ash is one of our most useful and versatile native tree species - it provides a valuable habitat for the likes of woodpecker, owls and nutchatches as well as a myriad of insects.
Because it's so strong and durable it has long been used for timber and for making things like furniture. But Ash Dieback is seriously threatening that,
Once a tree is infected the disease is usually fatal or weakens the tree so badly it is susceptible to other fatal fungi.
Dr Mark McMullan has been working on the Ash Dieback project at the Earlham Institute on the Norwich Research Park for four years.
His task was to establish the genome of the disease - essentially mapping its DNA.
What he has found is that if the current invasive gene gets a chance to reproduce with other genes from outside Europe - particularly from Asia, it would mean many more losses.
"It may kill the majority of ash trees in Europe as we know it now. If just a few individuals arrived, as is the case, that would mean that there is a really good reason to prevent further invasions."
The key then is stop any more spores coming over here either airborne or through imports. The alternative is creating a dieback-resistant species.
The disease was first spotted in Europe in 1992. Over the next 20 years it spread west and was eventually discovered in this ancient woodland in Norfolk.
At Easton College in Norfolk many of their older trees are resistant to the disease and have been unaffected.
Ash tree are the third most common in the country and can live to 400 years if coppiced correctly. Time is of the essence to ensure we can fightback against this devastating fungus.