New research finds garlic kills slugs

September 12, 2003

It was worshipped by the ancient Egyptians, was said to keep vampires at bay, and is good for keeping you healthy.

Scientists from the University of Newcastle upon Tyne have now found the pungent herb garlic could win the costly worldwide war against slugs and snails as an environmentally friendly pesticide.

The findings are published in the current edition of the academic journal, Crop Protection*. Lead researcher Dr Gordon Port will speak about the effective alternatives to chemical pesticides, with special reference to slugs, at approximately 11am at the BA Festival of Science TODAY, Friday September 12 2003.

Laboratory tests on nine potential molluscicides - the technical term for substances that kill slugs and snails - revealed that a highly refined garlic product (ECOguard produced by ECOspray Ltd.) was one of the most effective killers.

The research was carried out at the request of the crop growing industry and sponsored by the Horticultural Development Council and the Department for Environment, Food and Rural Affairs. It provides scientific proof of garlic's pest controlling properties, and should help businesses developing new treatment products for widespread use.

The scientists, Ingo Schüder and Gordon Port from Newcastle University's School of Biology, suspect garlic may have an adverse affect on the creatures' nervous systems but say it is difficult to say exactly why they die without further investigation.

Garlic has long been used in 'companion planting' strategies for hundreds of years. Monks used to site garlic next to their vegetable crops to keep unwanted pests away.

Slugs and snails cause millions of pounds worth of damage as they munch their way through food crops and plants, particularly those in cool, temperate climates like those of the UK, Northern Europe and North West America. Even more millions of pounds are spent trying to control them - the estimated overall cost to the UK is around £30m.

Growers are increasingly seeking alternative solutions to traditional pesticides, however, as ever-tightening regulations governing the use of chemicals may mean that some products could be withdrawn.

Garlic is already being used in some products as a mollusc repellent but this research takes it a step further. Earlier work by Newcastle University also found that garlic kills slug eggs laid in the soil.

The Newcastle University scientists looked at how applying a liquid containing garlic extract to soil affected slugs and snails' movement through it. They also measured damage to a Chinese cabbage leaf. Garlic largely prevented the leaf from being eaten and killed a very high percentage of the creatures.

Tests also revealed that ureaformaldehyde, a chemical used in the manufacture of chipboard, was a very effective molluscicide.

Lead researcher Dr Gordon Port said:

"Nobody has really found a definitive solution to the problem of slugs and snails. There are lots of products on the market but the real difficulty is actually getting to them in the field. They are very well adapted to their habitat, live hidden away in the soil, and are coated with layer of mucus that can help protect them from substances.

"Farmers and growers have difficulty controlling them with conventional bait pellets, which are particularly ineffective in very wet or very dry weather. Poison baits can also be toxic to other creatures living in the soil, as well as birds and mammals such as shrews and field mice.

"We need to find new environmentally and cost-effective ways of controlling molluscs, and garlic could be our answer. The tests show that it is certainly a potent chemical where slugs and snails are concerned and if used appropriately we know it's mostly harmless to man because it is used as a cooking ingredient.

"We need to carry out more tests to find out its commercial potential. We want to find out how garlic affects other creatures living in the soil, the right concentration to use, how it affects the taste of food once it has been used on crops, and many other things.

Dr Port added the findings may be welcomed by organic gardeners looking for alternatives to pesticides. He said: "The research suggests that a home-made recipe of crushed garlic bulbs mixed with water could work on small-scale gardens."
* JOURNAL REF: Barriers, repellents and antifeedants for slug and snail control. Vol 22, Issue 8 1033-1038, September 2003. Copies of the paper are available from the University Press Office via email (PDF file) or fax (six pages).


Pictures of Dr Port with slugs and garlic available free of charge via ISDN from North News and Pictures tel 44-191-233-0223.

Notes to editors

1. Dr Port will give a presentation entitled 'No pests or no pesticides: is there a choice?' at the BA Festival of Science today, Friday September 12, between 9.30-12.30. The Festival is being held at the University of Salford from September 8-12.
2. WEB LINKS: Newcastle University School of Biology: BA Festival of Science:

Newcastle University

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