Pest Control: Slugs
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If there's one garden pest that's way too familiar to every Northwest
gardener, the slug is surely that one. These slimy, soft-bodied land
mollusks thrive in our cool, moist climate. The glistening trails they leave,
the big bites taken from the leaves of tender plants, the seedlings chomped
right to the ground, and the gaping, slimy holes in ripening tomatoes all are
signs of their handiwork.
A slug's body is mostly water, about 90%. The sticky, viscous slime it
secretes helps to protect its moist body from injury and drying out. It
slithers about on its muscular "foot," lubricated by slime. Slugs are most
active at night, though in damp weather they may be out during the day too.
There are many different species of slugs, varying widely in size, color, and
markings. Some are more destructive than others. The big green banana
slugs we often picture when we hear the word "slug" are actually relatively
harmless to gardens and flower beds. Many of the non-native slugs are
much more destructive and worthy of our anti-slug efforts.
gardener, the slug is surely that one. These slimy, soft-bodied land
mollusks thrive in our cool, moist climate. The glistening trails they leave,
the big bites taken from the leaves of tender plants, the seedlings chomped
right to the ground, and the gaping, slimy holes in ripening tomatoes all are
signs of their handiwork.
A slug's body is mostly water, about 90%. The sticky, viscous slime it
secretes helps to protect its moist body from injury and drying out. It
slithers about on its muscular "foot," lubricated by slime. Slugs are most
active at night, though in damp weather they may be out during the day too.
There are many different species of slugs, varying widely in size, color, and
markings. Some are more destructive than others. The big green banana
slugs we often picture when we hear the word "slug" are actually relatively
harmless to gardens and flower beds. Many of the non-native slugs are
much more destructive and worthy of our anti-slug efforts.
The Slug
Slugs are hermaphrodites - each one is both male and female. That means that each and every adult slug
out there is laying eggs and adding to the slug population. Several times a year, a slug lays two or three
dozen translucent white eggs, about the size of BBs. Eggs are usually laid in cool, damp, shady places such
as under boards or leaf piles. The eggs hatch in 10 to 20 days, and the hatchling slugs grow to adulthood in
about six weeks. A slug can live for several years, growing larger and more voracious every year, and
producing eggs the whole time.
out there is laying eggs and adding to the slug population. Several times a year, a slug lays two or three
dozen translucent white eggs, about the size of BBs. Eggs are usually laid in cool, damp, shady places such
as under boards or leaf piles. The eggs hatch in 10 to 20 days, and the hatchling slugs grow to adulthood in
about six weeks. A slug can live for several years, growing larger and more voracious every year, and
producing eggs the whole time.
Slug Control
Life Cycle
Gardeners are a pretty ingenious lot, and so there are a lot of methods of dealing with slugs, both
commercial and homegrown.
Bait: The most common method of getting rid of slugs is to put out slug bait. Bait attracts slugs to feed and
poisons them. Encircling plants with a line of bait can prevent slugs from reaching them. Commercial slug
baits are very effective, but are often toxic not only to slugs, but to people, pets, and wildlife, and care must
be taken in using them. One method is to cut a U-shaped notch in the rim of an empty plastic butter tub and
place it over the bait, weighted with a rock. This allows slugs to get in and eat their last meal, while
discouraging other animals. Pet-safe slug baits are also available. The active ingredient, iron phosphate,
kills slugs but is harmless to people and other animals.
Beer is a proven safe bait, typically used in a plastic tub or dish that's buried up to its rim in the soil. The
slugs are drawn to its smell, crawl in, and drown.
Baiting with an attractive but non-lethal bait, such as dry pet food, may be effectively combined with the
search and destroy method - draw all the slugs in with the goodies, and then physically destroy them.
Search and destroy: Go through the garden at dusk and physically destroy slugs. Impaling them with a
sharp stake is quick and easy. Salting also works, by drawing moisture out of the slug's body and
dehydrating it, but since salt isn't good for garden soil, it's best used sparingly. Search and destroy might
seem tedious and inefficient, but when you consider how many eggs each slug you remove would lay in its
lifetime, the results definitely add up over time. It's also just about the cheapest and safest method of slug
control possible.
Barricade: Put a barrier around your plants that slugs don't like to crawl over. Rough or jagged materials,
such as sandpaper or crushed egg shells, are sometimes effective. Sheets of used sandpaper can be cut to
fit around the stems or stalks of plants. Crushed eggshells may be sprinkled liberally around plants, and give
the added bonus of supplying a little calcium to the soil when the break down. Diatomaceous earth (the
fossilized shells of tiny marine plankton) is like shards of broken glass to slugs. Copper strips or copper wire
are said to work as well, giving slugs an unpleasant sensation a bit like what we'd get from chewing aluminum
foil. Make sure not to leave any gaps in your barricade for slugs to find their way around.
Eliminate breeding sites: Part of any good slug control strategy is keeping them from being hatched in
the first place. Slugs lay their eggs in dark, damp places - under boards, wood piles, leaves and yard debris,
mulches, etc. Keep debris cleaned up, and avoid storing wood, cinder blocks, and such on the ground as
much as possible. Periodically check any remaining slug havens for clutches of eggs and destroy them and
any adult slugs you find there. Use bait or barricade methods to keep slugs away from mulch around plants.
Decoy plants: Plant rows or blocks of plants that are especially attractive to slugs, to draw them away from
your crops. Marigolds are a favorite. This is a good strategy to combine with search and destroy - draw
the slugs to your decoy plants, and finish them off!
commercial and homegrown.
Bait: The most common method of getting rid of slugs is to put out slug bait. Bait attracts slugs to feed and
poisons them. Encircling plants with a line of bait can prevent slugs from reaching them. Commercial slug
baits are very effective, but are often toxic not only to slugs, but to people, pets, and wildlife, and care must
be taken in using them. One method is to cut a U-shaped notch in the rim of an empty plastic butter tub and
place it over the bait, weighted with a rock. This allows slugs to get in and eat their last meal, while
discouraging other animals. Pet-safe slug baits are also available. The active ingredient, iron phosphate,
kills slugs but is harmless to people and other animals.
Beer is a proven safe bait, typically used in a plastic tub or dish that's buried up to its rim in the soil. The
slugs are drawn to its smell, crawl in, and drown.
Baiting with an attractive but non-lethal bait, such as dry pet food, may be effectively combined with the
search and destroy method - draw all the slugs in with the goodies, and then physically destroy them.
Search and destroy: Go through the garden at dusk and physically destroy slugs. Impaling them with a
sharp stake is quick and easy. Salting also works, by drawing moisture out of the slug's body and
dehydrating it, but since salt isn't good for garden soil, it's best used sparingly. Search and destroy might
seem tedious and inefficient, but when you consider how many eggs each slug you remove would lay in its
lifetime, the results definitely add up over time. It's also just about the cheapest and safest method of slug
control possible.
Barricade: Put a barrier around your plants that slugs don't like to crawl over. Rough or jagged materials,
such as sandpaper or crushed egg shells, are sometimes effective. Sheets of used sandpaper can be cut to
fit around the stems or stalks of plants. Crushed eggshells may be sprinkled liberally around plants, and give
the added bonus of supplying a little calcium to the soil when the break down. Diatomaceous earth (the
fossilized shells of tiny marine plankton) is like shards of broken glass to slugs. Copper strips or copper wire
are said to work as well, giving slugs an unpleasant sensation a bit like what we'd get from chewing aluminum
foil. Make sure not to leave any gaps in your barricade for slugs to find their way around.
Eliminate breeding sites: Part of any good slug control strategy is keeping them from being hatched in
the first place. Slugs lay their eggs in dark, damp places - under boards, wood piles, leaves and yard debris,
mulches, etc. Keep debris cleaned up, and avoid storing wood, cinder blocks, and such on the ground as
much as possible. Periodically check any remaining slug havens for clutches of eggs and destroy them and
any adult slugs you find there. Use bait or barricade methods to keep slugs away from mulch around plants.
Decoy plants: Plant rows or blocks of plants that are especially attractive to slugs, to draw them away from
your crops. Marigolds are a favorite. This is a good strategy to combine with search and destroy - draw
the slugs to your decoy plants, and finish them off!
| Banana Slug |