Mites - Pests of Ornamental Trees, Shrubs and Flowers - page 416

LIFE HISTORY
In greenhouses this species is active throughout the
year, breeding continuously whilst conditions remain
favourable. The mites are light-shy and tend to occur on
the young, succulent tissue of host plants. All stages
(eggs, larvae, quiescent nymphs and adults) shelter
within leaf folds, amongst leaf hairs and between bud
scales. As the tissue ages and hardens, the mites move
to younger, more suitable feeding and breeding sites,
commonly invading the still-furled leaves and unopened
flower buds. The mites may also spread from plant to
plant, particularly if leaves or shoots or adjacent hosts
overlap, but they rarely if ever wander over the soil or
the greenhouse staging. There are several overlapping
generations annually, mites passing from egg to adult in
about 2-3 weeks at temperatures of 20-25ºC; the rate of
development is much reduced at lower temperatures,
the egg stage becoming particularly protracted.
Although males occur, typically during the summer
months, they are usually greatly outnumbered by
females and reproduction is mainly parthenogenetic.
There are also several overlapping generations annually
on outdoor plants, populations reaching a peak in
August or September, but breeding usually ceases
completely during the winter months.

DESCRIPTION
Adult female: 0.14-0.2 mm long; whitish and
translucent, but often greenish or yellowish; body very
broad and oval (cf. Phytonemus pallidus ). Adult male:
0.11-0.17 mm long; whitish and translucent; body short
and broad, but tapered posteriorly; legs long, the hind
pair relatively stout. Egg: 0.11 × 0.07 mm; flattened,
smooth ventrally; several rows of large, white,
mushroom-like tubercles dorsally. Larva: similar to
adult but smaller and 6-legged.

LIFE HISTORY
The mites feed mainly on the underside of leaves but
also invade unopened or unfurling buds and other plant
tissue. Female mites, that greatly outnumber males,
normally live for about ten days, each depositing up to
50 eggs. Breeding is rapid in warm conditions, with
eggs hatching in 2-3 days and larvae feeding for four
days at normal greenhouse temperatures. The quiescent
nymphal stage is passed entirely within the bloated
larval skin. Adult males often carry female nymphs
around, holding them aloft with a genital sucker.

DAMAGE
New growth of infested plants becomes stunted and
discoloured, and is often shiny, brittle and distorted. On
some hosts, including cyclamen, flowers are malformed
and unopened buds may drop off. Heavily infested
plants may be killed.

DAMAGE
Infested foliage become brittle, discoloured and
crinkled, the margins of young leaves often rolling
tightly inwards; flower buds are also affected. Attacked
plants are stunted and young growth significantly
distorted; when infestations are severe, leaves, flower
buds or complete plants may be killed. Mites on
Michaelmas daisy plants, especially Aster novi-belgii ,
cause severe scarring of flower stems, affected 'flowers'
being converted into rosettes of small, green leaves.

Steneotarsonemus laticeps (Halbert) ( 1127 )
syn. Tarsonemus approximatus Banks
Bulb scale mite
An important pest of Hippeastrum and forced
Narcissus ; also associated with other members of the
Amaryllidaceae, including Eucharis , Scarborough lily
( Vallota purpurea ) and Sprekelia . Present in several
parts of Europe, including England, Germany, Ireland,
the Netherlands, Poland and Sweden; also found in
North America.

Polyphagotarsonemus latus Banks ( 1124-1126 )
Broad mite
A tropical and subtropical pest which, in temperate
countries, infests a wide variety of greenhouse plants,
including ornamentals such as African violet
( Saintpaulia hybrida ), Begonia , busy lizzie ( Impatiens ),
Chrysanthemum, Cyclamen, Dahlia, Gloxinia, Fuchsia,
Gerbera , ivy ( Heder a), Hibiscus , Japanese aralia
( Fatsia japonica ) and stock ( Matthiola ). Well
established in Europe, but less frequently reported than
formerly.

DESCRIPTION
Adult female: 0.2 mm long; light brown and
translucent; gnathosoma broader than long; palps
directed inwards; hind legs thin, each terminating in a
long seta. Adult male: similar to female but smaller,
and with robust hind legs. Egg: 0.1 mm long; oval,
whitish and translucent. Larva: similar to adult but
smaller and 6-legged.