Biology Reference
In-Depth Information
992
Metallus gei
(Brischke) (
992-993
)
Geum leaf-mining sawfly
Generally common on wild and cultivated
Geum
, and
frequently a pest in gardens and nurseries. Widely
distributed in Europe.
DESCRIPTION
Adult female:
3.5-4.5 mm long; body mainly black
but the abdomen partly brown; hind legs mainly white.
Larva:
pale greenish white, with a dark head,
prothoracic plate and anal plate.
LIFE HISTORY
Adult females of this parthenogenetic species occur in
May or early June, with a second generation in July and
August. The larvae are leaf miners, each forming an
expansive, light brown blotch on the upper side of a
fully expanded leaf of geum. The larvae feed from June
to July and from August to September or October, fully
grown individuals eventually pupating in cocoons in the
soil. In contrast with many other leaf miners, larval frass
does not accumulate in the mine but is ejected through
a small slit in the wall of the gallery.
992
Mine of geum leaf-mining sawfly (
Metallus gei
).
993
DAMAGE
Infested plants are disfigured by the conspicuous mines.
There are often several mines in each infested leaf and,
if attacks are severe, plants are seriously weakened.
Monophadnoides geniculatus
(Hartig) (
994
)
syn.
Blennocampa geniculata
(Hartig)
Geum sawfly
A generally common pest of
Filipendula
and
Geum
; also
attacks
Rubus
. Eurasiatic. Widely distributed in Europe.
993
Larva of geum leaf-mining sawfly (
Metallus gei
).
994
DESCRIPTION
Adult:
5-6 mm long; stout-bodied and mainly black.
Larva:
up to 14 mm long; head greenish yellow; body
green to dark green, with numerous white, branched
spines.
LIFE HISTORY
Adults occur in May and early June, females depositing
eggs in the underside of leaves of host plants. The larvae
feed from late May to early July. They then enter the soil
and spin cocoons, individuals eventually pupating and
adults emerging in the followings spring. There is just
one generation annually.
994
Larva of geum sawfly (
Monophadnoides geniculatus
).
DAMAGE
Larvae bite out large, irregular holes in the foliage; such
damage is often extensive, and heavily infested plants
are seriously disfigured and weakened.
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