More than four-fifths of people cannot identify an ash tree from its leaves and almost half cannot recognise an oak, a survey has revealed.

Members of the public are being encouraged to report signs of diseases that are threatening British trees, such as ash dieback, as part of efforts to tackle infection that could wipe out millions of trees.

But many people fail to identify some of the UK's most common trees that are at risk, a poll for the Woodland Trust suggests.

Only 17% of those shown an ash leaf could say what tree it came from, despite the high profile of Chalara ash dieback, which experts have warned could have the same effect on ash trees as Dutch elm disease had on UK elms.

And 57% could identify an oak, one of the country's most common trees. Oaks are at risk from disease such as acute oak decline, which causes bleeding and lesions on stems and tree death.