Biology Reference
In-Depth Information
SLUGS AND SNAILS
Slugs and snails are often important pests in gardens
and nurseries, attacking seedlings and herbaceous plants
such as Anemone , bell flower ( Campanula ),
Doronicum , Gladiolus , Hosta , hyacinth ( Hyacinthus
orientalis ), Iris , Narcissus , Petunia , primrose ( Primula
vulgaris ), Rudbeckia , strawflower ( Helichrysum ), sweet
pea ( Lathyrus odoratus ), Tagetes , tulip ( Tulipa ), violet
( Viola ) and various lilies. Slugs and snails feed at night,
and often then cause severe damage to seedlings, young
shoots, foliage and flowers. Such damage is sometimes
confused with that inflicted by caterpillars and various
other pests, but slime trails (if not the pests themselves)
on or in the immediate vicinity of attacked plants
readily betray the identity of the true culprits.
development until the following spring. Juvenile slugs
are similar in appearance to adults but smaller and
usually paler. They take anything from five months to
two years to reach maturity, the rate of development
varying from species to species and according to
conditions.
Several species are responsible for damaging
ornamentals; these include the garden slug ( Arion
hortensis ), the field slug ( Deroceras reticulatum ) and
various keeled slugs. The garden slug is a relatively
small (25-30 mm long), tough-skinned species, with a
rounded tail; the adults are mainly black above
and yellow or orange below. The field slug is larger
(30-40 mm long), soft-bodied and mainly yellowish
brown, with a distinctly pointed tail and a short dorsal
keel at the hind end. Both of these species readily attack
the aerial parts of plants. Keeled slugs, such as
Tandonia (
Slugs ( 1149-1150 )
Unlike snails, which usually hibernate during the winter
months, slugs breed throughout the year and remain
active in all but the coldest and driest of conditions.
Their translucent, often pearl-like eggs are deposited in
groups in the soil or amongst surface vegetation. The
eggs usually hatch within a few weeks but those
deposited during the winter might not complete their
Milax ) budapestensis , are characterized by
the presence of a distinct dorsal ridge that extends from
the mantle to the tail. Unlike other slugs, they feed
mainly below ground level, often boring into bulbs,
corms, rhizomes and tubers of ornamental plants; they
also damage plant roots.
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1149
1150
1149 Slug damage to flower of Narcissus .
1150 Field slug ( Deroceras reticulatum ).
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