A decade after ash dieback was found in the UK, there is still a real threat of importing other diseases with a “similarly devastating” impact, conservationists warn.

The disease, which causes leaf loss and crown dieback and can lead to tree death, could wipe out up to 80% of our country’s native ash trees, as they have not evolved natural defences against the fungus originally from Asia.

It was first spotted on imported trees in a nursery in Buckinghamshire in February 2012 and identified in the countryside in East Anglia in October that year, after spreading through Europe.

The Woodland Trust said the disease can spread through wind-blown spores, but many infected ash trees were also imported before a ban in October 2012, speeding up the process of ash dieback taking hold in the UK.

And the charity warned little had changed since ash dieback arrived, with weak and ineffective biosecurity for imports running the risk of other emerging diseases arriving here and causing catastrophe – just as the UK tries to ramp up its tree-planting efforts.

Alisha Anstee, lead policy advocate for tree health and invasive species at the trust, said the UK had become heavily reliant on imports for tree saplings in recent decades, because it had been cheaper.

The Government’s focus has been on border controls and inspections, but if a pest or disease is undetected, or difficult to spot at certain times of the year, it will still get through, she warned.

“There’s still a real threat we could be importing other diseases that have a similarly devastating impact as ash dieback has had,” she said.

She said the UK had ambitious targets to create 30,000 hectares (75,000 acres) of new woods a year as part of its climate and nature targets, but it needed to be done responsibly.

“It should be a concern now: we don’t want to import any diseases that mean we have to fell hundreds of thousands of trees in the next 10 years.

“We need to be planting responsibly now, we don’t want to find ourselves in a situation where we are now with ash dieback.”

There are 127 plant pests and disease that are considered to be a high risk to the UK, with 47 of them predicted to cost £1 billion each, the trust warns.

Ash dieback alone is predicted to cost £15 billion, killing off trees across the country, and altering landscapes where it is one of our most common trees.

It will have knock-on impacts for wider wildlife, particularly for the 44 species only found on ash, the Woodland Trust said, although there is hope that some ash trees are tolerant to the disease.

The woodland charity, which now only uses UK and Ireland-grown seeds and saplings from accredited nurseries, wants to see action from the Government to acknowledge the threat posed by imports.

Ms Anstee called for Government funding for expansion grants for UK nurseries, along with access to labour and ensuring a market for what British businesses produce – for example by contract-buying trees in advance through public funding for woodland creation schemes.

Protecting trees from pests and diseases is a key part of our approach to biosecurity, and we are acting swiftly and robustly to manage threats

On the charity’s own land, ash dieback’s impact has been highly variable, even to the extent of different parts of a single woodland site suffering different levels of damage, according to Mark Feather, UK estate manager.

The Woodland Trust has taken a precautionary approach to the disease in its woods, choosing not to pre-emptively fell infected trees if they do not pose a health and safety risk, as that is where resilience will be found.

The charity is also having to deal with other diseases, such as Phytophthora ramorum which kills trees including larches.

And if the invasive beetle emerald ash borer makes it to the UK, that could wipe out the remaining trees that had shown resilience to ash dieback, it warns.

Mr Feather warned of the threat tree disease posed to the climate and nature targets, saying: “We could be losing millions of old trees to pests and diseases at the same rate as planting millions of new trees, we’ll never get there.”

He said there was a need to create a resilient landscape with a diversity of species, managing tree health and new diseases alongside new planting – and being responsive to problems rather than trying to plan too rigidly for the future.

An Environment Department (Defra) spokesperson said the Government had committed to providing funding to support UK nurseries, had invested in plant import inspections and was continuously reviewing threats and action needed to address them.

They said: “Protecting trees from pests and diseases is a key part of our approach to biosecurity, and we are acting swiftly and robustly to manage threats.

“Since ash dieback was first detected in the UK, the Government has invested just under £7 million to advance our scientific understanding, have conducted the world’s largest screening trials and planted the first national archive of tolerant ash trees.”