A silver streak of slime, on or near your plants, is a dead give-away that you have a very much alive slug eating its way through your garden.

It is best to know the life-cycle of slugs and the conditions they favor in deciding how to control this most common garden pest.

Our cool and moist climate is home to several varieties of slugs ranging widely in color and size. They glide around on a single foot that excretes a mucous trail to abet movement and consequent attack on tender plants and shoots. Slugs are heavily reliant on moisture and most active during damper seasons, preferring to come out at night or during wet, overcast days to eat.

Each slug has both female and male reproductive organs and can produce up to 400 eggs annually. Laying eggs can happen any time of year but decreases during drier and colder weather. Eggs are 1/8 to 1/4 inch, round or oval, are either transparent or opaque and are laid in batches among moist fine soil.

Hatchlings migrate to feed on roots. About 90 percent of slugs are underground at any time but will migrate to feed on favored plants. They can live from 12 months to two years and depending on moisture and available food can begin reproducing as young as three months.

When the weather is warm and dry, slugs like to hide beneath things that will keep them cool and moist, avoiding dry and dusty areas entirely.

Take action

There are many options for controlling slugs. Since they predictably hide under objects, remove anything in and near your garden that will provide shelter, such as rocks, boards and compost piles, as an important first step.

Weeds and tall grasses will harbor slugs so it is best to border your garden with dry, abrasive materials such as cinder, gravel, wood chips or sand.

Some gardeners find it useful to set traps. There are various ideas for attracting slugs into many types of traps, mostly involving a small pool of stale beer.

The concept is that fermenting liquids bait them and since slugs can’t swim, they drown. It can make for a fun conversation but not so fun to clean and maintain these traps.

Hunt them down. Armed with a flashlight at night or by turning over strategically placed boards in the morning, you can hand pick them with gloves on, of course. Drown them in soapy water and dispose of them in the garbage receptacle.

Do not put them in your compost pile as they are considered meat and therefore not compostable.

Slugs’ natural predators are garter snakes, frogs and birds, including domestic ducks and geese.

Chemical solutions

If slugs outnumber and survive their natural predators, your beer traps and hunting excursions, a chemical control may be desired. There are two types of pesticide available for slugs; both should be used as directed.

Metaldehyde has been used to kill slugs by home gardeners for decades. In bait, granule and spray forms, products with metaldehyde also are toxic to unintended wildlife, birds and pets.

In recent years other chemical products have become available that contain iron phosphate, which is considered non-toxic and applied the same, has proven to be just as effective as metaldehyde at killing slugs.

For best performance in controlling slugs, begin treatment early in the spring before garden plants appear. Baits will be more tempting when spring conditions draw slugs out of hiding but before tender new shoots are available to consume.

Bait them again in the fall, first as egg production is expected to increase with moist weather, and then again later in the fall to get the next generation missed with the first treatment.

Armed with all of this slimy knowledge, the hunt for the silver streaking slug will be more successful. Happy hunting!

Join us next week to learn more about, “Deer: A normal part of the environment.”

Michele Mangiantini is a Washington State University-certified, Clallam County Master Gardener.