Agriculture Reference
In-Depth Information
Frankliniella occidentalis
(Pergande)
Western flower thrips
plants. Damage is usually restricted to the leaves
and is of only minor significance. However, on
strawberry (in common with certain species of
thrips that may feed within the flowers at blos-
som time) this pest has been implicated in the
development of distorted fruitlets, especially on
late-season cultivars. Individuals are distinguish-
able from
Frankliniella occidentalis
(above) on
the basis of microscopical features.
In the 1980s, this polyphagous non-indigenous
thrips appeared in considerable numbers on
glasshouse plants in England and various other
parts of Europe, including France, Germany,
the Netherlands and Scandinavia, having been
introduced accidentally from abroad, mainly on
chrysanthemum cuttings. Significant infesta-
tions have occurred on aubergine, cucumber, to-
mato and various other plants (including many
ornamentals) and attempts to eradicate the pest
have not proved successful. In warmer parts of
Europe, this pest is also now established on vari-
ous outdoor hosts, including fruit trees and vines.
Adults and nymphs cause distortion, silvering and
speckling of leaves and flowers
(Plates lc and Id),
and damage from even a relatively small number
of individuals is often extensive. The thrips are
also implicated in the transmission of important
plant viruses, such as tomato spotted-wilt virus.
Kakothrips pisivorus
(Westwood)
Pea thrips
This widely distributed thrips is a generally com-
mon pest of legumes, especially pea and broad
bean crops growing in allotments and private
gardens. The surface of infested tissue becomes
silvery and flowers sometimes fail to develop;
plants and pods are also malformed. Heavily in-
fested plants are severely stunted and crop yields
may be reduced. Most damage tends to occur
under dry conditions during June and July;
late-sown or late-maturing crops are particularly
susceptible. In the British Isles, attacks are often
especially common in the south and east of
England.
BIOLOGY
This species breeds continuously under suitable
conditions, and the life-cycle is completed in 2-3
weeks at normal glasshouse temperatures. There
are two nymphal instars, after which individuals
drop to the ground to complete their develop-
ment in the soil. Although adults and nymphs are
sometimes observed on the exposed surfaces of
leaves and flower petals, they are of secretive
habit and occur more frequently on the under-
side of leaves, or hidden within the shelter of
flowers and beneath bud scales.
BIOLOGY
Adults occur from May to July, when they
infest the flowers, foliage and pods of pea and
bean crops. Eggs are inserted in rows along the
stamen sheaths or in other floral tissue; they
hatch in about 10 days. Nymphs are very active
and are usually most numerous in June or July.
Individuals feed for up to 3 weeks before becom-
ing fully grown. They then enter the soil, where
they overwinter. The new adults appear after
nymphs have passed through brief propupal and
pupal stages. There is a single generation each
year.
DESCRIPTION
Adult
1-2mm long, pale yellow to brownish-
yellow;
antennae
8-segmented;
forewings
with a
complete row of setae along veins I and II (cf.
onion thrips,
Thrips tabaci,
p. 93).
Egg
0.2mm
long, pearly-white.
Nymph
golden-yellow;
eyes
reddish.
DESCRIPTION
Adult female
1.5-2.0 mm long, blackish-brown
to black, and somewhat flattened;
antennae
8-
segmented, the third segment yellow;
legs
mainly
brown, with yellow tarsi;
forewings
dark brown
but clear basally;
abdomen
distinctly pointed
Frankliniella intonsa
(Trybom)
Flower thrips
This generally common, polyphagous species
is sometimes damaging to outdoor broad-leaved
