Biology Reference
In-Depth Information
236
237
236
Western flower thrips (
Frankliniella occidentalis
) damage
to flower of
Chrysanthemum
.
237
Flecking on petals of
Chrysanthemum
, caused by western
flower thrips (
Frankliniella occidentalis
).
Frankliniella occidentalis
(Pergande) (
236-237
)
Western flower thrips
An important polyphagous thrips of American origin.
Now widely distributed in Europe, originally having
been introduced on imported
Chrysanthemum
cuttings
in the 1980s. Ornamentals commonly infested in
northern Europe include
Achimenes
, African violet
(
Saintpaulia hybrida
), busy lizzie (
Impatiens
), cape
primrose (
Streptocarpus hybrida
),
Chrysanthemum,
Cineraria, Cyclamen, Gerbera, Gloxinia, Pelargonium
and vervain (
Verbena hybrida
). An important vector of
plant virus diseases. Attempts to eradicate the pest from
Europe were unsuccessful.
DAMAGE
Thrips cause silvering and spotting of tissue as well as
noticeable blanching, especially on petals. Significant
damage is caused by a relatively small number of
individuals. Infestations also lead to noticeable
distortion of host plants. The effects of tomato spotted
wilt virus, transmitted by this pest to various hosts
(including
Chrysanthemum
and
Gloxinia
), are often
severe.
Frankliniella intonsa
(Trybom)
Flower thrips
This yellowish to reddish-brown, 1.2-2.8 mm long, flat-
bodied thrips infests a wide range of ornamentals, and
causes minor damage to the foliage and petals.
Infestations are most often reported on heather (
Erica
).
Unlike the following species, the front projection of the
head is triangular and there are eight pronotal bristles.
DESCRIPTION
Adult:
2 mm long; pale yellow to brownish yellow;
antennae 8-segmented; distinguishable with certainty
from closely related species only by microscopical
examination.
Nymph:
translucent to golden yellow;
eyes reddish.
Propupa:
white, with short wing cases.
Pupa:
white, with long wing cases.
Frankliniella iridis
(Watson)
Iris thrips
Infestations of this widespread species sometimes occur
on
Hippeastrum
and
Iris
. Nymphs and adults cause
silvering of foliage and pale speckling of flower petals.
Female thrips occur throughout the year, and hibernate
during the winter months; males and nymphs are
present during the summer and autumn. There are
several generations each year. Adult females
(1.5-1.7 mm long) are dark brown and flattened, with
pale yellow (usually reduced) wings; the front
projection of the head is rounded, and there are six
strong pronotal bristles.
LIFE HISTORY
Although most frequently associated with
chrysanthemum, attacks also become established on
many other greenhouse plants. In favourable situations,
infestations also occur outdoors. The thrips infest both
surfaces of the leaves but tend to occur more commonly
on the underside, causing a noticeable scarring and
excreting tell-tale specks of black frass, a typical
symptom of thrips attack. They also occur commonly
beneath bud scales and between the calyx and petals of
open blooms. Breeding is continuous whilst conditions
remain favourable, the complete lifecycle occupying
about 2-3 weeks at temperatures of 20-30ºC. Pupation
occurs in the soil.
Search WWH ::
Custom Search