Imagine a Britain without vegetable patches, allotments or beautiful flower beds, where gardeners are unable to grow anything outside, knowing any plants will be ravaged by a foreign predator.

This is, admittedly, a worst case scenario, but still not an impossible one, says scientist Dr Ian Bedford, head of entomology in the John Innes Centre in Norwich. He is leading a group of scientists in a project to monitor sightings of the Spanish slug, Arion vulgaris, a particularly aggressive and large slug which breeds and eats at a faster rate than our native species and has so much slime on its body many native predators are put off.

Slugwatch.co.uk was launched a couple of weeks ago, asking people to report sightings. Within ten days, there had been 18,000 visitors to the site and more than 800 submissions, some reporting the Spanish slugs, Dr Bedford confirms.

This year has generally been a bad year for slugs. Late spring frosts killed off a lot of them, but this may just be offsetting the plague that could follow – we need late spring frosts and early winters to kill off juvenile slugs to keep numbers down.

He had evidence of Spanish slugs eating snails and even working their way through dog faeces and eating dead animals such as mice.

Growing plants which slugs don’t like may provide some solution for domestic gardeners, though.

“The plants which don’t seem to get attacked by slugs are the ones which have high levels of plant oils, such as rosemary, which has high levels of camphor, and lavender,” explains Dr Bedford.

Other plants not favoured by slugs include azaleas, pieris, geraniums, mature shrubs and conifers, although Dr Bedford points out that last year Spanish slugs ate his buddleia and rudbeckias.

Contrary to reports, slug pellets will kill Spanish slugs but because of their voracious appetite they will eat a lot of slug pellets before they die, he notes.

It’s better to go on slug patrol early morning and at dusk, preferably after rain, as these huge slugs are highly visible, and pick them off before putting them into a bucket of water containing detergent which will cause them to sink, he advises. Then dispose of them and bleach the bucket to kill off any bacteria.

Slugs are nothing new to gardeners nationwide. On average a UK garden is home to more than 20,000 slugs and it is estimated that an acre of farmland can support more than 250,000 of the slippery creatures.

Now the rain has stopped, I shall venture into my garden, bucket in hand, searching for those slimy monsters... and perhaps you should do the same.