Slugs are nocturnal and the most telling clue that they are resident in your garden is the silvery trails they leave behind.
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I joke that I sold my last house because I found myself sharing the garden with a multitude of slimy slugs. That wasn’t really the reason for moving … at least not the only one.
Slugs are gastropods, not insects. They are related to snails and clams rather than flies or beetles. They should not be confused with pear slugs which are insects (the larval form of a sawfly), found on cotoneaster, pear, mountain ash and other related woody plants.
Slugs are nocturnal and the most telling clue they are resident in your garden, aside from the damage, is the silvery trails they leave behind. Their preferred habitat is damp — which unfortunately describes a lot of territory.
Growing up on the West Coast where slugs come in many shapes, sizes and colours, I particularly remember the banana slug named for its resemblance to said fruit in colour and size. Thankfully, in most Saskatchewan gardens, you’ll typically only encounter the diminutive grey garden slug (Deroceras reticulatum): small, 1-2 cm long, dark to light grey, shiny and, of course, slimy. Don’t let their size fool you. What they lack in size, they can rapidly make up in numbers, laying 200-300 eggs at a time. And in numbers, they are voracious, decimating leafy plants (e.g. hostas) and many other garden plants including root crops like potatoes and carrots (unfortunately not dandelions in my experience).
Selling your home is not a guaranteed or a long-term solution because slugs or their tiny eggs can move in from the neighbour’s yard, on plants from the nursery or your friends, on borrowed tools and even on the bottom of your shoes.
There are ways to fight back. Start by making your garden less hospitable by removing daytime hiding places such as wooden boards, bricks, stones, and garden gnomes. Remove all decaying vegetation throughout the season, especially in the fall.
Trapping slugs is a good next option. They are attracted to yeasty, fermenting odours. But don’t waste your beer: add a package of bread yeast to a cup of water sweetened with sugar, stir and set aside to bubble away for a couple of hours. Add an inch of the yeast solution to any shallow container (e.g. empty cat food or tuna tins). Place several in the garden in the early evening, about 10 feet apart. In the morning, empty the containers (hopefully filled with drowned slugs) and repeat. Another option is to place short boards in the garden. In the morning, just scrape any cowering slugs off the bottom sides into a bucket of soapy water or straight into the garbage. Repeat. Another effective trap is an upside-down rind of a half grapefruit. Slugs can’t help themselves and will be found munching away in the morning on the inside. Simply dispose of rind, slugs and all. Repeat.
There are a number of other control options, most of which are safe to use around the home, children and pets.
Slugs are said to avoid wood ash and coffee grounds (some coffee shops give bags of grounds away for free). If nothing else, the ash and grounds will help enrich your soil.
To a slug, crushed baked egg shells sprinkled around the garden act like razor wire, as does diatomaceous earth (DE), a powdery substance composed of sharp fossilized microscopic hard-shelled algae or diatoms. There are several registered insect and slug control products that are 100 per cent DE (e.g. Safer’s Insectigone). Pool-grade DE is not effective in controlling slugs and other insects because it has been exposed to high heat during processing, altering it significantly. Wear a face mask to avoid breathing in the fine particles when sprinkling them around the garden. Reapply after heavy rains.