Giant ‘ cannibal ’ slugs are set to wreak a trail of destruction in gardens across Britain , experts have warned . Two mild winters in a row have created the perfect conditions for Spanish slugs - an horrific , aggressive species which grows up to six inches long - to expand their territory . The species , nicknamed the cannibal slug because of its tendency to feast on the remains of dead relatives , was first spotted in this country in 2012 . The giant Spanish slug , pictured , was first spotted in the UK in 2012 and is now starting to take hold . Sightings have since been reported in Norfolk , Suffolk , Essex , Kent , London and Hampshire . But this year it is expected to tighten its hold on the country and spread even further . Dr Ian Bedford , the expert who first identified the species three years ago , warned that it is likely to thrive after two very mild winters . ‘ If this warm weather continues and we do not have any cold spells before May we could see very high numbers of the Spanish slug this year , ’ he said . Dr Bedford , head of entomology at the John Innes Centre in Norwich , said the slug - which officially is called Arion vulgaris and originates in southern Europe - can not survive extreme cold temperatures . Common native slugs , although less aggressive , are much better at surviving cold conditions . Experts say it is too early to know whether common varieties will have a boom year , because the volumes of rain we see this spring and summer will be much more closely tied to their fortunes . The winter of 2012/13 saw several cold snaps , blizzards and frosts , which hit the new population of Spanish slugs hard . But the intervening two winters have been much warmer , particularly in southern England which has barely seen any snow in 24 months . The average temperature in England for December , January and February this year was 4.4C ( 39.9F ) , and the year before was even warmer at 5.8C ( 42.4F ) . The average English winter temperature is 4.2C ( 39.6F ) . Slug expert Dr Ian Bedford , pictured , said Britain was on course for record numbers of Spanish slugs . The slug , pictured , is not able to survive extremely cold winters and frozen conditions . The Spanish slugs , which are thought to have made it to the British mainland on imported vegetables , have been recorded feeding on dead mice , meat and each other and can withstand up to 20 slug pellets . They also devour garden plants - terrible news for gardeners . Unlike native species , they produce so much slime that birds and hedgehogs tend not to eat them . They also produce twice as many eggs as native slugs , so are more likely to increase their populations and expand their territory quickly . Dr Bedford said : ‘ If you spot these in your garden the best way to deal with them is to drown them in a bucket of soapy water , add a bit of household bleach , and then bury the remains 18 inches deep . ‘ If they spread it could really affect British farmers . We found in 2012 that farmers were having to replant oil seed rape because of these slugs . ‘ If we allowed large numbers to develop in our gardens it will be a problem for commercial growers to control them because they are only allowed to use a certain limit of pesticides each year. ’ Anna Platoni , entomologist at the Royal Horticultural Society , said it is too early to tell how much of a problem normal native slugs will be this year . ‘ Although native slug damage can be predicted by the temperature and humidity , it is really the conditions over spring and summer that are important , rather than over the winter , ’ she said . ‘ They tend to overwinter in sheltered spots so are protected from the worst of the weather. ’ Sarah Fuller , marketing director at Wyevale Garden Centres added : ‘ Slugs and snails are a real problem for gardeners , making this hobby and pastime a true 24-hour activity . ‘ Last year gardeners removed up to 4,000 slugs a month . ‘ It ’ s likely more slugs have survived this winter so gardeners will be fighting larger numbers and need to use really effective methods . ’
The Spanish giant slugs arrived from the continent during 2012 . It is believed they managed to sneak into Britain aboard a vegetable lorry . A succession of mild winters has left the country at risk of an infestation .