Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 113

Heliothrips haemorrhoidalis (Bouché)
syn. H. adonidium Haliday
Glasshouse thrips
This tropical or subtropical thrips is a frequent
greenhouse pest in temperate regions, infesting many
ornamental plants including azalea ( Rhododendron ),
Begonia , calla lily ( Zantedeschia aethiopica ),
Chrysanthemum, Fuchsia and rose ( Rosa ), as well as
ferns, orchids, palms and vines. Under favourable
conditions, breeding continues throughout the year, but
this insect cannot survive northern European winters in
unprotected situations. Adults (1.2-1.8 mm long) are
dark brown, with an orange tip to the abdomen and pale
yellow antennae, legs and wings; the fore wings are
narrow, with few and very short setae on the veins; the
antennae are 8-segmented, with the terminal segment
needle-like; the tarsi are 1-segmented. The yellowish-
brown nymphs produce a reddish fluid, that is deposited
in large drops on the surface of host plants and upon
which brown fungal growths develop. In addition,
feeding by adults and nymphs results in a brownish,
silvery or whitish spotting of leaves and flowers.

spine-like setae. This and other species of Limothrips
commonly give rise to the term 'thunder-flies'.

Parthenothrips dracaenae (Heeger) ( 238 )
Dracaena thrips
This subtropical species is widely distributed in
greenhouses in northern Europe on plants such as Citrus,
Croton, Cycas, Dracaena, Ficus, Howea, Stephanotis
and Tradescantia . As often noted on ornamental rubber
plants ( Ficus elastica ), affected foliage becomes
extensively damaged, both the upper and lower surfaces
developing distinctive silvery patches. Adults ( c . 1.3 mm
long) are yellow or brown, with a strongly reticulated
head and thorax; the antennae are 7-segmented, with the
terminal segment needle-like; the fore wings, which lack
a costal fringe of hairs, are very broad and hyaline, with
a reticulate pattern, and distinctly banded with brown;
the legs are brown, with yellow tibiae and tarsi; the tarsi
are 1-segmented.

Kakothrips pisivorus (Westwood)
syn. K. robustus (Uzel)
Pea thrips
A widespread and common pest of legumes, including
sweet pea ( Lathyrus odoratus ), but rarely of significance
on ornamentals. Adults occur from May to July or
August, infesting and causing a silvering of the foliage,
flowers and pods. There is a single generation each year,
nymphs developing during June, July or August. When
fully fed, the nymphs enter the soil, where they
overwinter; new adults appear in the spring. Adults
(1.5-2.0 mm long) are blackish brown and flat-bodied,
with dark brown, basally clear, fore wings; the antennae
are 8-segmented, with the third segment yellow.

238

Limothrips cerealium Haliday
syn. L. avenae Hinds
Grain thrips
This mainly black-bodied thrips often appears in vast
numbers during July or August, at about the time that
cereal crops are ripening. The adult females may then
invade greenhouses, to appear on crops such as
Chrysanthemum . Damage caused by other thrips
(particularly onion thrips, Thrips tabaci , p. 123) is often
seen on greenhouse-grown ornamentals at the time of
invasion, and grain thrips (which breed only on cereals
and grasses) is then sometimes mistakenly assumed to
be the harmful species. Unlike onion thrips, grain thrips
has 8-segmented antennae, the head is longer than broad
and the tenth abdominal tergite bears a pair of stout,

238 Dracaena thrips ( Parthenothrips dracaenae ) damage to
leaf of Ficus elastica , viewed from above.