The National Bee Unit has confirmed a sighting of the Asian hornet in the Tetbury area of Gloucestershire – the first time the insect has been found in the UK.
The species poses no greater risk to human health, but does represent a threat to native honey bees.
Work to identify, destroy and remove any nests is already underway, including a three-mile surveillance zone around Tetbury.
A local control centre will coordinate the response and bee inspectors will search the area with infrared cameras and traps.
NFU acting chief horticulture adviser Chris Hartfield said the first finding of this "new serious" pest of honeybees represents a "worrying time" for bee farmers and beekeepers.
"Robust control measures are already in place, so let’s hope it’s a limited outbreak that can be quickly contained and controlled," said Mr Hartfield.
Defra’s deputy director for plant and bee health, Nicola Spence, said: "We have been anticipating the arrival of the Asian hornet for some years and have a well-established protocol in place to eradicate them and control any potential spread.
"It is important to remember they pose no greater risk to human health than a bee, though we recognise the damage they can cause to honey bee colonies.
"That’s why we are taking swift and robust action to identify and destroy any nests.
"We remain vigilant across the country, working closely with the National Bee Unit and their nationwide network of bee inspectors."
'Essential to maintain exciting variety'
CLA Senior Policy Adviser Jonathan Baker said pollinating insects are "essential to maintain the exciting variety of plants and wildlife in the UK and play a vital role in food production."
"While it is good news that the Asian hornet poses no great risk to human health, the impact that its arrival on UK shores could have on our pollinators is cause for concern.
"We look to Defra to implement a swift and effective containment plan to ensure that this invasion of a non-native species has limited effect on our native flora and fauna.
"We encourage anyone who believes they have found an Asian hornet nest to avoid getting too close but report the sighting straight away," Mr Baker concluded.
The hornet found in Tetbury is currently undergoing DNA testing at the National Bee Unit in North Yorkshire to help establish how it arrived in the UK.
The hornet arrived in France in 2004 and is now common across large areas of Europe. It was discovered for the first time in Jersey and Alderney this summer.
It is believed the species will not be able survive in the North of the UK due to colder winters.
Anyone who believes they have found a nest should not go near it and report it to firstname.lastname@example.org. The cost of eradication on private land will be met by APHA.