The National Allotment Society - National Society of Allotment and Leisure Gardeners Ltd

Organic Slug Control

Organic Slug Control

The most popular method of slug and snail control used in the garden is slug pellets. The pellets are manufactured from cereal and yeast that lures the slugs and snails to them and they contain a poison that kills the slugs and snails after they have consumed the pellets.

There are three main types of poison used in slug pellets.

  • Metaldehyde – this is considered a low toxic poison. It causes the slug or snail to swell up eventually leading to death. It damages the mucus cells resulting in the production of masses of slime which causes dehydration of the slug or snail. The slug/snail isn’t always killed outright but becomes immobilised and is prevented from returning to the safety of its daytime shelter. Metaldehyde doesn’t have to be ingested to be effective it can also kill slugs/snail through contact.
  • Methiocarb – (BANNED from late 2014) this is about ten times more poisonous than metaldehyde. It poses a greater risk to wildlife. It takes longer to break down which makes it a more persistent hazard. It can also kill other insects including slug eating beetles. It is also damaging to earthworms.
  • Ferric phosphate –this is considered to be a safe, low toxic alternative to metaldehyde. It is a stomach poison and kills the slugs/snails after they have ingested it. Ferric phosphate damages the digestive tissue causing the slug/snail to stop eating. The pellets are flour based that break down quickly. Ferric (iron) phosphate is found in food products. Some organisations still want more research carried out on the use.
  • The Soil Association will not certify any pest and disease control products. The use of ferric phosphate would only be permitted by the Soil Association on a highly restricted basis, following a special application by an organic producer.

Although there aren’t any slug pellets that can be used in the organic garden it doesn’t mean that the garden will be completely overrun with slugs and snails meaning that all of our plants reduced to slimy stumps. Slug pellets aren’t very effective at controlling slugs. They will only kill around 10% of the slug and snail population in the average garden.

Organic garden management relies on prevention always being better than a cure. In the organic garden we use a system known as Integrated Pest Management Control sometimes referred to as IPM. IPM systems use a wide variety of controls to keep on top of pests and diseases. They depend upon the gardener taking steps to build up food chains within the garden that will attract suitable pest predators into the area.

Drainage

Moist conditions provide ideal conditions for slugs. The structure and drainage of the soil can be improved through the appropriate use of cultivation and by adding garden compost. Incorporating sharp sand or horticultural grit into poorly drained areas which can be identified as slug breeding sites can also be effective. The problem may serious enough to require the installation of land drains to take the surplus water away.

Predatory insects.

Providing the right habit for natural enemies, especially ground beetles, will help to control slugs. Beetles, especially carabids are extremely effective at reducing slug populations and they feed voraciously on slug eggs, as well as the slugs themselves. Field margins and beetle banks provide ideal habitats for predatory beetles. It is worth mentioning that spring cultivation will reduce the beetle population, whilst autumn cultivation has little effect on their numbers.

Encourage birds

Many birds, particularly blackbirds and song thrushes, will eat considerable numbers of slugs and snails.  By providing bird boxes, winter feeding areas, trees and hedgerows, also any uncultivated areas will all help to maintain and improve biodiversity. Hens are also effective at cleaning up an area both pre and post harvest.