are among the most easily recognized pests of
Pennsylvania gardens. Who hasnít seen the glistening
transparent slime trails left in the wake of their
passage through the hosta bed? Or encountered them on
a wet sidewalk? Or come across them in the woodpile or
under some stone or debris in the garden?
Slugs are mollusks, gastropods
to be exact. They lack the hard spiral shells of their
snail cousins. They move on their bellies, actually a
large foot muscle, secreting a slimy mucus trail as
they do. The mucus trail facilitates their passage
over uneven terrain and protects their soft underbelly
from abrasion over sharp surfaces. It also helps them
adhere to otherwise slippery surfaces. As the trail
dries, it hardens to a clear cellophane-like ribbon
betraying the passage of the pest. Slugs also secrete
mucus over their entire bodies for protection and to
prevent drying out.
The slug species found in
Pennsylvania are drab in color, brown and gray or a
combination of the two being the usual colors. Gray
garden slugs are often small, ĺ to 1 inch in length.
However, some species, such as the dusky slug or the
leopard slug, can grow much larger, up to 2 to 4
inches when extended. This latter, Limax maximus, is
the large grayish-yellow slug with black markings we
see so often.
Emerging or hatching in the
spring when the temperatures begin to reach above 40ļ
F., slugs prefer cool, moist surroundings.
Consequently they come out to feed at night and spend
the day resting beneath logs, stones, leaves and plant
debris or anywhere else that helps them retain their
body moisture and does not get warm enough for them to
begin to dry out.
The eggs are small BB-sized
clear balls laid in a hollow in the earth or under
logs. You may have come across these while preparing
the garden since they are often laid in the same
environment that the adults favor. The young that
emerge in the spring become sexually mature by late
summer. Each individual possesses both male and female
organs, so once they have mated both can lay eggs.
Mature individuals lay between 10 and 40 eggs. The
adults can live up to three years, wintering over in
fallen plant debris.
Even if you donít see the
actual creature, the slime trail and the shredded leaf
that it leads to are sufficient to tip you off to the
presence of slugs in the garden. They feed on many
kinds of plants grown in the garden, be it a flower
garden or a vegetable garden. They especially like
strawberries and hostas. This should come as no
surprise as these plants offer the cover and moist
environment the mollusks prefer.
While it is nearly impossible
to eliminate slugs entirely, it is possible to control
them and the damage they inflict. The easiest control
measure is to make sure there is nowhere for them to
take shelter during the day. Clean up any garden
debris, organic material, leaves, wood, etc. that will
afford shelter. Remove flat stones or bricks and
boards from the garden area if possible. Make sure
compost piles and sites for waste materials are at a
distance from the garden. When mulching, apply no more
than 3 inches of mulch. This will retain enough
moisture for the plants but dry sufficiently to
dissuade slugs from hiding in it.
There are chemical products on
the market that will control slugs and snails. Be sure
to read the labels carefully and follow the
instructions for use as these products can be harmful
to children, pets and beneficial insects. Unless you
have a serious infestation, organic measures are much
cheaper and can be just as effective.
If there are only occasional
individuals, these can simply be picked off the plant
and disposed of in a can of soapy water. Or you can
trap them and dispose of the ones you catch. Setting
out a board or a damp piece of burlap or newspaper in
the evening will attract them beneath it. In the
morning remove the slugs and drop them in a can of
For some reason slugs are
especially drawn to beer and other yeast containing
liquids. One effective way to trap slugs in the garden
is to bury a half-full can of beer up to its rim or
set out a throw-away aluminum pan filled with some
beer near where slugs are damaging plants. The slugs
will be attracted to beer and die happy.
Another solution is to
surround the planting with diatomaceous earth. This
product may be picked up at most garden stores. It
consists of the sharp shells of small sea animals.
This dries and rips the foot of the slug and,
consequently, they avoid crossing it. It loses its
effectiveness when wet, so it must be renewed. And
while copper barriers are reputed to be effective,
they are more expensive and must extend into the soil
as well as about 6 inches above it.
Slugs are food for many
creatures normally found in our gardens: ants, some
beetles and their grubs, earwigs, garter snakes, toads
and turtles. So donít be hesitant to encourage these
friendly species to take up residence in your yard.
If all else fails, you can
always choose plants slugs do not like. Instead of
soft-leaved, juicy plants like lettuce, hosta,
marigolds, strawberry and many vegetables, substitute
fuchsias, geranium, impatiens, lavender, and
nasturtium as these are resistant to slug damage.
Slugs also avoid fragrant herbs with stiff leaves such
as rosemary and thyme as well as grasses and many
woody ornamental plants.
Read other articles about controlling insects & garden pests