Biology Reference
In-Depth Information
1120
Eriophyes tiliae lateannulatus
Schulze (
1120
)
syn.
E. tiliae rudis
Nalepa
This subspecies is associated with small-leafed lime
(
Tilia cordata
), producing nail galls that are much
smaller (up to 5 mm long) than those formed on large-
leafed lime by
Eriophyes tiliae
; the mites are sometimes
regarded as a distinct species.
ULMUS
Aculus ulmicola
(Nalepa) (
1121
)
Elm bead-gall mite
An often abundant species, responsible for the
development of tiny (
c
. 1 mm diameter) bead-like galls
on the upper surface of the leaves of elm (
Ulmus
). Adult
females overwinter under the bud scales, invading the
underside of the unfurling leaves in the spring and
inducing the formation of the distinctive galls. Breeding
continues within the galls throughout the late spring and
early summer; at the height of development each gall
contains up to 200 or more mites. Infestations are often
very extensive, and vast numbers of galls often occur on
each infested leaf. As a result, the foliage of affected
branches develops a distinctly roughened appearance.
Heavy infestations have a detrimental effect on host
plants, reducing their resistance to severe weather
conditions and leaving them more susceptible to
other disorders. Mites inhabiting these galls are
c
.
0.17 mm long, with about 55 abdominal tergites and
characteristic, two-branched feather-claws.
1120
Galls of
Eriophyes tiliae lateannulatus
on leaf of
Tilia
cordata
.
1121
1121
Galls of
Aculus ulmicola
on leaves of
Ulmus
.
Eriophyes filiformis
(Nalepa) (
1122
)
Elm leaf blister mite
This southerly-distributed species causes the
development of pouch-like galls on the leaves of elm
(
Ulmus
), including amenity trees. The galls are much
larger than those formed by the previous species but are
usually less numerous; they cause slight distortion of
the foliage but shoot growth is not affected. The mites
are
c
. 0.17 mm long, with about 90 abdominal tergites.
1122
YUCCA
Cecidophyopsis hendersonii
(Keifer)
A North American species, introduced into Europe on
imported
Yucca
plants. In Europe, the pest was
first reported on greenhouse-grown blue-stem yucca
(
Y. guatamalensis
) in Scandinavia. The upper surface of
affected fronds appears dusted with whitish powder.
Older infested leaves develop brown markings and
eventually turn yellow and die. The causal mites are
relatively stumpy and lack setae on the prodorsal shield.
1122
Galls of
Eriophyes filiformis
on leaf of
Ulmus
.
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