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Mosquito invasion threatens a plague on Ulster

Ulster has been invaded by mosquitoes - and the diseases they carry could pose a heightened risk to human health as climate change starts to bite.

Scientists in Northern Ireland are keeping an eye on mosquito levels after higher than usual numbers were reported last year.

The news comes after researchers in the USA warned that food crops could be ravaged this century by an explosion in insect pests numbers caused by rising global temperatures.

After investigating the fossil record of a previous period of global warming, they warned that numbers of leaf-eating insects are expected to surge because of temperature rise. The team believes the insects migrated north from tropical regions and also ate more because the rising concentration of atmospheric carbon dioxide made leaves less nutritious.

Scientists in Northern Ireland monitoring the midges that can carry bluetongue disease are also keeping tabs on other insects that could pose a future threat.

Dr Archie Murchie, a Senior Scientific Officer with the Agri-Food and Biosciences Institute in Hillsborough, said there are no figures for mosquito levels but they have increased.

The insects could potentially carry a range of diseases that pose a risk to human health, including the killer West Nile virus, which has infected thousands of people in the USA.

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"When we started to monitor midges for bluetongue, part of the remit of that project is to look at other insect vectors that can carry diseases," he said.

"Last year mosquito numbers were very high - a lot of people contacted us because they had been bitten.

"A lot of people don't realise we have mosquitoes. They think it's a tropical or sub-tropical insect. We have a number of species here which we need to keep an eye on. There is potential not just for animal diseases, but human diseases as well."

The gardener's enemy - greenfly - could also flourish as Ulster experiences milder winters, Dr Murchie said. These aphids also have the potential to cause serious damage to wheat, barley and orchard crops.

"Aphids are one of the biggest economic pests. If there was an increase in temperature and CO2 you'd end up with more aphids," he said.

"One of the factors that play a role is milder winters. If you have a mild damp winter, a lot more of the insects survive.

"In terms of global warming there are two problems. The first is invasive insects coming in from warmer climates. The second is the insects here that are pests - if you've got a milder winter you get greater survival during the winter.

"Trying to predict what would happen in the future is very difficult. We are certainly seeing more invasive species coming in, but whether it's driven by climate change or it's just the fact that people are moving foodstuffs around more, we don't know."

Dr Murchie says there are a number of economically damaging insects that have made their way into the UK and could soon reach Northern Ireland, including the harlequin beetle, a lily beetle and a leaf miner which damages chestnut trees.

"There is a whole array of them that are coming in all the time. They are coming in cut flowers - they are coming in aquarium plants, that sort of thing," he says.

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