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Slugs

There are many species of gastropod molluscs, literally ‘stomach foots’. They are essentially snails without shells and a major cause of damage to seedlings in both farm and garden. The UK, with its mild and wet climate, is particularly prone to slug infestation. Each cubic metre of soil may have 200 or more slugs within it. The grey field slug is the most serious plant destroyer and, when it breeds in spring, each slug produces 300 offspring.

Slugs work both underground and on the surface. They have thousands of sharp teeth and can destroy potato crops without ever emerging at ground level. Because they have no shell they are particularly prone to drying out. This accounts for why they emerge after rain, or watering, and at night. Many methods of control depend on their lifestyle and its response to moisture.

Slugs may be misunderstood by gardeners. Most species eat decaying vegetable matter and are therefore part of the natural recycling system. Unfortunately a few of them go for healthy plants, especially young seedlings. They may also have a memory, returning to the same patch of seedlings night after night. Their preference for young seedlings gives another handle on management.

The word from the experts is that growers in the UK should not attempt complete eradication of slugs, but rather aim to manage their numbers.

The easiest and most natural forms of management include:

Grow seedlings on until they are as large and strong as possible before planting out

Deliberately encourage the presence of natural predators such as frogs, toads, hedgehogs, song birds, nematodes and runner ducks.

Provide moist shelters for slugs during the day eg moist bark, upturned grapefruit and remove the slugs regularly

More active management systems include:

Making fences around plants eg with plastic bottles over individual plants, or a slug collar made of a bottomed-out flowerpot with a slit up the side. These can be supplemented with copper tape or various gels to inhibit slug movement.

Anything that dries out the environment around the plants eg baked and crushed egg shells

Adding nematodes to the soil – this works for a six week period and then needs repeating but will see young seedlings through the vulnerable period. Available online or from garden centres.

Using chemicals:

The most common slug pellets contain metaldehyde, which is dangerous to animals and may be contaminating our water supplies.
Some use is now being made of iron sulphate, which may be more environmentally friendly but not yet approved for organic growing.

A serious paper on slugs and their control can be found here

If you have the stomach for it and would like to see the more amazing side of slugs you can watch a film of their extraordinary mating habits here