Slugs In Your Compost

After a spell of wet weather your garden – if it’s anything like mine – will teem with slugs that have sprung from seemingly nowhere. The truth is they were there all along, biding their time until conditions became hospitably damp. They’ll lurk in crevices and under bricks, stones, and pieces of wood – anywhere that enables them to stay moist while the surrounding soil dries out.

Compost piles are another place you’re likely to find slugs, and for many gardeners this poses two interesting questions: How do I get them out of there, and Do I really need to?

Why You Have Slugs in Your Compost

Most slugs are generalist herbivores that will creep through your garden, tasting a bit of this, sampling a bit of that, whether it’s the shoulders of radishes peeking up out of the soil, those dead annual weeds you hoed off, your prized strawberries, or a little crop of mushrooms that have spontaneously appeared in your lawn.

The slugs that are most attracted to your compost heap are a little different however. They tend to be specialist detrivores – creatures that feed on dead and decaying plant matter – and they love chomping on all the wilting plants and soggy kitchen waste that can be found in the average compost heap.

If you regularly find more than a handful slugs in your compost, this is an important clue – your compost may be too wet. To fix the problem, add more ‘browns’ such as dry leaves, cardboard, sawdust or shredded wood to balance out the ‘greens’ from your kitchen and lawn, and turn it to introduce more air into the heap.

The type of compost bin you use also comes into play, because some are better at allowing air to circulate than others. I use both pallet composters and ‘Dalek’ style plastic bins. In the pallet composters, I only ever find congregations of slugs when I cover them with old rubble sacks or a tarp to protect them from winter rains. But almost every time I lift the lid from one of the Daleks I’m sure to see several fat, well-fed slugs hanging around near the top.

Slugs in Compost

So this brings us to the second question: Do I need to remove slugs from my compost bin?

Some gardeners fear that spreading compost on the garden will spread slugs and slug eggs around, but if you dig down you should find that the slugs are mainly interested in the freshly added organic matter near the top. The finished compost lower down contains less food for them, so is of little interest. Added to that, eggs are likely to be eaten by predators such as beetles, or otherwise squashed by the weight of the compost.

It’s also accepted wisdom that a thriving compost heap is unlikely to result in a garden invasion by hordes of hungry slugs. It makes sense – if the compost bin is reliably providing food and habitat, only the most adventurous slugs are likely to leave it on the off-chance they can find better pickings elsewhere.

Short of individually picking them out and killing them, there’s really no way to get rid of slugs in your compost bin. You should never use slug pellets or other pesticides in your compost because they will also kill other beneficial creatures that are vital to the composting process. Far better to accept them as part of your composting team. Along with other detrivores, compost heap dwelling slugs are providing an important service, munching through your kitchen and garden waste and turning it into valuable soil improver. I actually remove slugs from my garden and add them to the compost heap. I suppose I’m a bit of a softie at heart, but to my mind it’s better putting them to work than resorting to murder (or wasting good beer)!

Carnivorous Slugs

Not all slugs are vegans. For instance, the leopard slug (Limax maximus) is an unfussy omnivore which has been shown to reduce numbers of harmful slug species. Using their radula (denticle-covered tongue) these ghastly gastropods will not only chow down on vegetable matter, they will also rasp away at dead and decaying animals including other slugs and slug eggs. Don't have nightmares...

Bugs, Beneficial Insects and Plant Diseases

Slug Guide