If you have a garden, you are guaranteed to have slugs and snails. Not
surprisingly, they are some of the most troublesome pests a garden is ever likely to have.
They have a particularly destructive effect on young seedlings in spring when both
plants and pests emerge. Later in the year, underground slugs eat their way into growing potatoes
while their counterparts above ground tackle those juicy
strawberries. Meanwhile, snails munch holes in your flourishing hostas and
devastate your salads and cabbages.
They tend to remain hidden during daytime, especially in dry conditions, doing
most of their damage at night when conditions are cooler and moister. They will delight in humid, rainy
spells.
Slugs are active throughout the year provided the temperature is at least
5 degrees centigrade (41 fahrenheit). Snails, on the other hand, are more sensitive to the cold and
are likely to hide under garden debris such as logs and pots. Over winter they seal themselves
into their shells with mucilage to reduce water loss.
Slugs come in a variety of sizes, colours and species. Unlike snails, they have no (or, more
accurately in some cases) virtually no shell. Both are hermaphrodites, carrying male and female sex organs,
but they have to pair up to achieve sexual reproduction. They lay up to 50 eggs at a time which
hatch into tiny, miniature versions of the adult. They take between one and three years to
mature.
Both slugs and snails will eat dead and live plants - and also a lot of miscellaneous
material found in the garden such as fungi. A few types of slug are predators, feeding off
earthworms underground. As well as the damage they leave behind, the presence of slugs
and snails is obvious from the slimy trail they leave behind that dries into a glistening,
reflective sheen.
Several natural predators will tackle them, including thrushes, slowworms,
hedgehogs and shrews. Anything that encourages these creatures will be advantageous to your plants
as well. There are also some insect predators such as beetles and fly larvae.
Most potential predators are put off by their slimy nature, however.
One way of dealing with them is to take a flashlight out into the garden after
dusk and collect them - disposing of them as you see fit. However, picking on the big ones seems to
have the unfortunate effect of stimulating the smaller slugs and snails left behind into comparatively rapid growth.
Another approach is to provide barriers between susceptible plants and the
pests. Removing the cap from a plastic drink bottle and cutting the bottom off gives you
a cheap and instant one-plant cloche that can give protection until your delicate seedling
has grown to a less vulnerable size.
On a larger scale, it is possible to cover the soil around a group of plants with abrasive
material such as sharp sand, soot or commercial products which slugs and snails find
unpleasant. But remember that slugs can travel under the surface of the soil and that rain and
other weathering can quickly reduce the effectiveness of the material.
Slugs and snails can be given a merry death with a beer trap. Commercial
versions are available but a plastic container or jam jar sunk into the ground and partly filled
with beer is perfectly adequate to attract the creatures which drown in the liquid. Keep the top of the container
about half an inch above the ground so that beneficial insects do not fall in as they cross the garden.
Slug pellets are available from garden centres. These are chemical and can
poison birds and animals as well. If you feel you must use them, make sure that they are covered
in some way (e.g. a flowerpot dish with one edge slightly raised) so that the slugs and snails can access
them but other creatures are unable to do so.
Slugs in Compost Bins
It is quite normal to find a selection of wildlife in your compost bin, including slugs. The large ones, in particular, are attracted by decaying vegetable matter. While they are munching away on your vegetable waste, they are not paying any attention to more important items in the garden. Many people regard them as a natural part of the composting process.
If you add any poisonous material to kill them it may also kill beneficial bugs and microbes in the compost. That could include salt if you put in a significant amount. My inclination would be to leave them alone.
In theory, the compost should eventually get hot enough to kill slug eggs and drive away the adults. This requires a sufficient volume and regular turning. In practice a domestic compost bin may not achieve this temperature, especially if you are regularly adding vegetable waste (which is the whole point of them). Regardless, you will eventually accumulate enough compost to think about putting it on the garden. The adult slugs will probably have died or gone by that stage. At that stage it would be best to spread the composted material for a while where sun, birds, etc. can get to the eggs and prevent them hatching out.
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