Biology Reference
In-Depth Information
1151
Snails
(
1151
)
Particularly on calcareous soils, snails are troublesome
pests of ornamentals, attacking seedlings as well as the
young shoots and foliage of established plants. Species
most likely to cause damage in gardens and nurseries
are banded snails (
Cepaea
spp.), the garden snail
(
Cornu aspersum
) (syn.
Helix aspersa
) and the
strawberry snail (
Trichia striolata
). Strawberry snails
often cause extensive damage to seedlings being raised
in cold-frames.
1151
Garden snail (
Cornu aspersum
).
EARTHWORMS
When burrowing in the soil, some species of earthworm
regularly deposit excreted soil (worm casts) on the
surface, their activity being greatest in the spring and
autumn. Worm casts are a particular nuisance on fine
lawns, and are especially unwelcome on bowling
greens, golf greens and tennis courts. The species most
often causing a problem are
Allolobophora longa
and
A. nocturna
. On balance, however, earthworms are
beneficial and important components of the soil fauna.
BIRDS
In the winter and spring, birds frequently attack dormant
or opening buds of trees and shrubs, affected shoots
often developing with any remaining blossoms
restricted to the extreme tips. Bud stripping is
sometimes of considerable importance on almond
(
Prunus dulcis
), crab-apple (
Malus
), flowering cherry
(
Prunus
),
Forsythia
, lilac (
Syringa
) and
Viburnum
carlesii
, and is usually caused by bullfinches. Other
birds, including blue tits, chaffinches and greenfinches,
also damage dormant buds but are usually of only minor
importance.
House sparrows are notorious for the damage they
cause to
Crocus
, primrose (
Primula vulgaris
), sweet pea
(
Lathyrus odoratus
), violet (
Viola
) and various other
flowers, attacked flowers being torn to pieces and the
stripped petals left lying on the ground, a typical sign of
bird damage. House sparrows also invade greenhouses
and plastic tunnels. They also steal seeds from newly
sown lawns, and cause disturbance in dry seedbeds by
taking dust baths.
In autumn and winter, various birds feed on the
berries or fruits of trees and shrubs, the colourful
displays on ornamentals such as barberry (
Berberis
),
Cotoneaster
, firethorn (
Pyracantha
), holly (
Ilex
) and
Sorbus
often being depleted. Birds responsible for such
damage include blackbirds, fieldfares, jays, redwings
and woodpigeons.
The aesthetic value of birds usually far outweighs the
damage they cause, and many are of direct benefit to the
gardener or nurseryman. During the spring and summer,
for example, insectivorous species such as tits, warblers
and wrens destroy vast numbers of insect pests,
including many of those attacking the foliage or flowers
of ornamental trees and shrubs. Some birds, notably
blue tits and great tits also feed on overwintering insects
and mites hiding beneath bud scales or within bark
crevices. Others, including rooks, seek out soil pests
such as leatherjackets, swift moth larvae, vine weevil
larvae and wireworms; large numbers of slugs and
snails are also killed by birds.
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