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Halting the invasion of the Asian hornet

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ASIAN yellow-legged hornets – Latin name Vespa velutina – have a powerful sting and the ability to cause irreparable damage to the Island by killing honey bees and other beneficial pollinator insects.

An Asian hornet

Asian hornets don’t just prey on honey bees, they have an equally voracious appetite for all pollinating insects from bumble bees to dragon flies. Considering one secondary nest can contain up to 200 queens and 6,000 workers, and each hornet can devour 50 insects in one day, if the local population grows as fast as it has in other locations it will have a devastating impact on the agricultural industry and gardeners.

Pollinating insects play a crucial role in the human food production chain. Along with birds, bats and other small mammals, they are responsible for pollinating about one-third of the food consumed by people around the world. They also sustain ecosystems and produce natural resources by helping plants reproduce.

The first sighting of an Asian hornet was recorded in Jersey in August 2016 and last year 11 nests were found and destroyed by a task force led by the Island’s beekeepers working closely with the Environment Department.

The aggressive insect has also colonised Guernsey, Alderney and Sark.

So far there have only been three confirmed sightings and one nest found in the UK which places the Channel Islands at the forefront of British efforts to keep the Asian hornet at bay.

Jersey has been more affected by Asian hornets than anywhere else in the British Isles, with 11 nests detected last year and a further ten discovered here since 23 April this year.

In 2017, nests were located in the east of the Island with the first discovered at Fliquet in St Martin. This year the Asian hornet has extended its range to establish nests in St Mary in the north and La Moye at Jersey’s south-west tip with sightings of individual insects at Corbière and in St Ouen.

The hornet’s rapid colonisation of the Island, reflecting it’s spread across western Europe, is being studied by experts from the University of Exeter who are spearheading the UK government Department of Food and Rural Affairs efforts to check its progress and European countries where the pest has also established a foothold.

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As honey bees are the Asian hornets’ preferred prey the Jersey Beekeepers Association members were the obvious choice to lead the Island’s Asian hornet task force.

It is their job, working with the Environment Department, to find and destroy nests – and preferably before queens and worker hornets move on to establish new colonies.

The stages of a population explosion

Stage one: The cycle begins in the autumn when a queen sets off, impregnated with next year’s offspring, to hibernate over the winter.

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Stage two: When she wakes up in the spring, usually in late March, she lays her egg and builds a nest – known as a primary nest – and waits for her brood to hatch and pupate into worker hornets.

Stage three: When the colony reaches around 50 workers, it has outgrown the nest. So, led by the queen, it moves on to build a larger or secondary nest.

John de Carteret, vice-president of the Jersey Beekeepers Association, says the local Asian hornet population is currently between stages two and three. And this, he warns, is a crucial time when old and new nests must be located and destroyed otherwise the consequences for the Islands’ growers and ecology could be dire.

Of the ten nests found in the past two months, all have been primary ones, with the first six confined inside. However, the last four, discovered between 29 May and 18 June were all active with queens and workers flying outside.

Mr de Carteret says this could mean that secondary nests are in the process of being established.

He wants to get across to Islanders the scale of the serious threat Asian hornets pose for the Island, and everyone else if they are left unchecked.

‘It is in everyone’s interest to be observant and let us know where nests are and when they think they sight a Asian hornet,’ he said. ‘It would be disastrous for growers if they were allowed to proliferate in the thousands and I am not referring to individual insects but the number of nests.

‘The Asian hornet appears to be pretty well established around the Island this year. If each queen follows the life cycle of the Asian hornet it can conservatively produce at least 200 new colonies or nests this year.

‘There is evidence gathered from monitoring two nests discovered in 2012 in Galicia in Spain, that shows by four years later the population [in that region] had grown to 10,647 nests.’

Closer to home the invasive pest has established a sizeable population in nearby Normandy, since it was first recorded in St Malo in 2011.

Last summer more than 3,000 nests were discovered and destroyed in Normandy’s La Manche region – which at its closest is just 14 miles from the Island.

How you can help

Members of the public are asked to look for nests in outdoor porches, sheds, garages and outbuildings and high up in trees. However, nests have also been found in Jersey in a compost heap, a hedgerow and in undergrowth.

A primary nest is small, slightly larger than a tennis ball, and a secondary nest is a larger spherical-to-pear-shaped nest, the size of a backpack.

The Asian hornet is smaller than the more common native European hornet. It measures between 17 mm and 32 mm.

Also known as yellow-legged hornets, the mid body is predominantly black/dark brown with a velvety finish. The rear section of the body again appears velvety with brown segments bordered with a fine yellow band.

The head is black with an orange/yellow face and the legs comprise a brown upper segment with a orange/yellow segment.

Sightings, ideally with a photograph, should be emailed to environment@gov.je or by calling 441600.

Paula Thelwell

By Paula Thelwell
author

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