Beekeepers have been placed on red alert by a government warning that the UK is about to be invaded by the Asian hornet - a species whose favourite food is the honey bee. The aggressive hornet - Vespa velutina nigrithorax - hunts bees to deadly effect. Just a handful of the dark-bodied, yellow-legged hornets can destroy a bee colony in two hours. They have already spread across France and into Spain, and are “highly likely” to reach Britain, according to the Non-Native Species Secretariat. The Asian hornet, which can grow to 3cm long, was introduced to France in 2004, in a shipment of pots imported from China. It has swiftly adapted to the European climate. A single colony can produce more than 15,000 hornets. Earlier this month there were sightings in Belgium. While the secretariat does not put a figure on the impact the marauding hornets could have on crops, it states: “If the UK were to suffer a total loss of pollinators (not just honey bees) the cost is estimated to be £440mn per year.” The invading hornets are “very likely to survive eradication attempts” and will be a serious problem for beekeepers. The British Beekeeping Association has alerted members to prepare for the worst. It is calling on them to make beehive entrances smaller to deter the large hornets, use wasp traps, and report any sightings immediately. And Stuart Roberts, chairman of UK Bees, Wasps and Ants Recording Society, said: “We are on red alert for any sightings – There’s not a beekeeper in this country who is not aware that this thing is just on the other side of the Channel. We are all on the lookout.” Invasive species cost the economy £1.7bn a year, according to the department for environment, food and rural affairs. And the government is now drawing up plans to deal with the Asian hornet. A Defra spokesperson said: “The Asian hornet could spread across the UK in just a few years.” Norman Rabone, 66, a beekeeper from Gillingham, Kent, said: “Hornets are terrible killers of bees. They have a killer instinct.” Asian hornets usually build large nests in trees. As well as hunting honey bees, they eat other insects and feed on fruit and flowers. People are also at risk. In France, at least seven people were taken to hospital in 2009 after being attacked.