Bird-friendly ways to beat snails and slugs in NZ gardens

Eggshells are no barrier for a snail determined to attack your vege patch.
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Eggshells are no barrier for a snail determined to attack your vege patch.

There's nothing like the heartbreak of spending hours sowing, raising, planting and tending your favourite garden veges - only to see them munched to pieces by snails and slugs.

Blogs and any number of old wives' tales will tell you that a ring of crushed eggshells, spent coffee grounds or salt around your plants will protect them from marauding snails.

Others recommend strips of copper tape – in theory, snails won't cross the tape because it gives them an electric shock. But what actually works?

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Virgil Evetts tested various barriers around young seedlings and found eggshells were ineffective.
SALLY TAGG

Virgil Evetts tested various barriers around young seedlings and found eggshells were ineffective.

When the late Virgil Evetts tested some alternative pest control methods for NZ Gardener magazine, he found that snails effortlessly crossed a barrier of crushed eggshells and within minutes were eating the seedlings on the other side.

Virgil also advised against using table salt. It does indeed form a barrier against slugs and snails, but it also kills pretty much everything else, so don't be tempted to put it anywhere near your garden.

As for coffee grounds, I know from my own experience that this is a myth. I use waste grounds from the office coffee machine as mulch and in my worm farms. Snails and tiger slugs positively frolic in the grounds. 

These cutdown copper hot water cylinders are regularly scaled by snails - so it seems unlikely that copper rings are better.
BARBARA SMITH

These cutdown copper hot water cylinders are regularly scaled by snails - so it seems unlikely that copper rings are better.

Gardeners have told me they've had success with commercially available copper tape snail barriers. However, I'm suspicious.

I have several copper rings cut from hot water cylinders that I use for mini compost bins and moveable raised beds. The 40-50cm high copper sides are no barrier at all to snails and slugs and I often find clusters of them hiding under the rims. The copper is many years old and is well-oxidised so it may be that only new, shiny, unoxidised copper tape works. 

So which methods do work? You can buy proprietary slug pellets, such as Quash, which is a non-toxic alternative to regular pellets. Pellets are most effective in spring, when slugs and snails are leaving their winter shelter.

Many gardeners use beer traps to lure snails and slugs to their death.
MONIQUE FORD/FAIRFAX NZ

Many gardeners use beer traps to lure snails and slugs to their death.

Evetts tested out beer traps - where you fill a shallow container with dregs of your favourite bevvy - and found that they did work but only within a small area. 

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They are not reliable by themselves but might be useful as part of a more comprehensive slug and snail control strategy.

My proven method is time-consuming, but effective. Go snail hunting regularly at night with a torch and a bucket of warm water.

Every snail disposed of now won't be around to breed for the rest of the season. You'll soon find their regular haunts and can even make tempting places for them to hang out so you can gather them up easily.  

This upcycled butter container allows the slugs to access the pellets but keeps curious birds safe.

This upcycled butter container allows the slugs to access the pellets but keeps curious birds safe.

Half grapefruit skins placed upside-down are ideal.

Feed the corpses to the thrushes and blackbirds the next morning. They will be ever so grateful!

Get Growing reader Linden Johnson upcycles small plastic food containers into slug and snail traps.

"Here's how you make them: using scissors, cut a V notch in the wall  of the container base, put the lid back on, invert then secure with a rubber band, and place approximately 20 slug bait granules inside through the notch.

"Place the traps near young seedlings or where there is slug or snail damage. The advantage of this is that it gives you an idea of how many slugs and snails are about and also protects thrushes from being poisoned. Check traps daily, clean and rebait them as necessary. Happy hunting!" 

What methods of slug and snail deterrents have worked for you?

 - NZ Gardener

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