Snails - Mollusks out of water
Tim Gibb, Insect Diagnostician, Department of Entomology,
Snails are not insects but rather gastropods
and if the Greeks have their definitions right, gastropod means ‘stomach-foot’.
These animals are more closely related to clams and mussels than
they are insects. They are easily identified because of
the characteristic hard shell on their back and their single,
broad, muscular foot upon which they move about. Two pairs of ‘tentacles’ protrude
from the front end of the snail, the larger pair tipped with
eyes are for sight and the smaller, anterior pair for sensing
Snails may occur on a large number of plants
but generally require conditions that are moist and abounding
in decaying organic matter.
The brown garden snail, see photo, is
an introduced pest and is common throughout the nation. It
can live multiple years. It can survive the winter by
sealing itself off inside its shell by using a thick membrane
called an epiphragm (in case you were looking for an unusual
babies name). It
is active during the spring and summer and lays eggs in the soil
during the fall time.
Snails have a unique mouthpart that is used
to scrape and rasp the vegetation on which it feeds. This can result in either
holes or simply a discolored area of the leaf or stem where the
snail has eaten away the epidermal leaf tissue. In either
case the plant can become unsightly very quickly.
Many different cultural control methods have
been tried and many have been touted as being effective. Common among
these is the recommendation of using salt. When applied
directly it will immediately desiccate the snail and instill
a great sense of satisfaction within the applicator. The
snail quickly retreats inside its shell and squirms spastically
before shrinking up to near nothing. When used on the ground
around a plant, the salt will help keep the snails at bay, however,
avoid using enough salt to poison the plant or change the characteristics
of the soil.
Beer has been used in shallow trays or dishes
as bait for snails. The
fermenting liquid (wine works equally well) attracts the snails,
whereupon they crawl right into the saucer and apparently drown.
Drowning in beer may not be the most dignified death, but at
least they die with smiles on their little faces.
Wood ashes, certain soaps and copper foil
are also reported as effective barriers to keep snails out. Insecticides
usually have little effect on snails because snails are so dissimilar
to insects. Baits that include ‘iron phosphate’ or ‘Metaldehyde’ as
the active ingredient are labeled for snail control and can be
purchased at most garden centers. Placing these materials
during the late afternoon or evening (snails feed at night) and
under the canopy of the plant (sunlight breaks down the product),
preserves their effectiveness.
Hand picking snails is also an effective
means of control in localized areas. Snails congregate during the daytime under
boards or wet newspapers lying on the ground. This behavior
can be taken advantage of by congregating and then physically
destroying the snails.
Long-term controls depend upon reducing their
preferred habitat in some way. Reducing the amount of moisture and/or organic
matter by adjusting irrigation and or mulching activities can
be some of the most effective ways to control these little ‘one-footed,
shell toting stomachs’.