Environmentalists are urging Welsh gardeners to use greener methods to combat slugs and snails this summer.

Experts at the Centre for Alternative Technology in mid Wales are aiming to persuade growers to avoid reaching for the slug pellets and instead explore other options, including beer traps, egg shell barriers and even coffee.

Alan Shepherd is trialling different methods

Alan Shepherd, who works on the Bug-a-Slug Project at the Machynlleth centre, said visitors had provided many alternatives to the usual poisonous blue pellet option.

"We've had about 70 different ways of getting rid of slugs and we have brought them back to CAT to use in the garden," he said.

Traditional chemical-based repellents are disliked by conservationists because they can be eaten by wildlife and can cause environmental contamination.

Commercial growers also face problems because residue from the pellets is not permitted on food crops.

One method which has proved popular with many gardeners is leaving a saucer of beer near precious plants.

Precious plants can be ruined by snails and slugs

Slugs and snails are attracted by the smell, climb in for a drink, and then drown.

Other people who prefer not to kill anything choose to use broken egg shells or grit as barriers around their plants.

Slugs and snails avoid them because they are uncomfortable to cross.

Copper screens are also being tested as barriers. It is thought that the metal reacts with the slime secreted by the insect, causing a flow of electricity.

Frenzy

Last week, American scientists revealed they had stumbled on another secret weapon - caffeine.

A strong cup of coffee is enough to send the creatures into a writhing frenzy, followed soon by death.

The discovery was made by scientists at the US Department of Agriculture's Agricultural Research Service in Hawaii.

They were testing a caffeine spray against frog pests when they noticed slugs were dying.

Follow-up studies showed that a 1-2% caffeine spray was enough to kill snails and slugs.

Beer traps have proved popular

Even at concentrations about 100 times weaker, the slugs lost their appetite.

A cup of instant coffee contains about 0.05% caffeine, while brewed coffee contains more.

Lead researcher Dr Robert Hollingsworth says because caffeine is a natural product and is classified by the US Food and Drug Administration as safe, "It has potential as an environmentally acceptable alternative toxicant for the control of slugs and snails on food crops."

There is a catch. Caffeine at 2% concentrations can damage the foliage of plants or cause yellowing.

It may be possible to overcome this by mixing caffeine with a polymer, say the researchers, who report their findings in the journal Nature.

But not everybody is convinced that caffeine is environmentally friendly.

Some experts say it is potentially dangerous for plants and invertebrates.