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Adult- Gladiolus thrips emerge milky-white, but soon turn dark brown, except for the apical
portions of the legs which are lighter. The wings, brown apically and lighter basally, appear to be
darker with a grey band when folded over the back. This thrips is about 1.5 to 1.65 mm long.
Males are smaller slightly smaller and lighter in color than the females.
Egg- The eggs are opaque, white, kidney-shaped, and
about 0.34 mm long and 0.2 mm in diameter.
Larva- The larvae of the gladiolus thrips are light or pale
yellow with red eyes and are about 1.0 mm long when fully developed.
Pupa and Prepupa- The pupae move only when disturbed
and develop through 2 instars. The first instar (prepupa) has
short wing pads and the antennae project forward. The second
instar (pupa) has long wing pads and the antennae are folded
back onto the head. Both stages are dark orange with red eyes
and about 1.2 mm in length.
Fig. 166: Gladiolus Thrips, Thrips simplex (Morison), Thripidae, THYSANOPTERA
Distribution- Gladiolus thrips is now found wherever
gladioli are grown. However, it cannot overwinter out-of-doors in northern Europe and northern
Host Plants- The gladiolus thrips most seriously damages
gladioli, but is also a pest of iris, carnation, lily, narcissus,
freesia, amaryllis, tigerflower, poker plant, tomato, begonia,
primula, snapdragon, chrysanthemum, and geranium.
Damage- Plants severely infested with gladiolus thrips
have a spotted, bleached appearance (see Color Plate). Both
leaves and petals are fed upon and appear withered. If flower
buds are seriously damaged, the flowers fail to open. The
entire plant may become stunted.
Life History- Gladiolus thrips are believed to be an
introduced pest from Africa, where gladioli are native. The
thrips are brought into previously uninfested fields or greenhouses on infested corms. These
rather sluggish thrips can overwinter at any stage on stored corms or on plants growing
in greenhouses. Although the gladiolus thrips can maintain a
population outside during the summer, they cannot overwinter
outside in areas where the temperature consistently falls below 10° C.
These thrips have six stages in their life cycle: the egg, two
larval instars, two pupal instars and the adult stage. Females
deposit 100 to 200 eggs. Many times females greatly
out-number the males in a population and parthenogenesis
occurs. Parthenogenetic females produce eggs that develop
into males. Temperature greatly determines the duration of
each stage. During the warm growing season the development
of the gladiolus thrips can occur in about 2 weeks. With such
rapid development, the thrips can have nine or more
generations outside during the growing season. The eggs are
deposited in the leaves of gladioli or in the corms in storage.
Larvae and pupae can be found in the buds or leaf sheaths,
although the larvae often drop to the ground to transform into
the quiescent pupae. Adult gladiolus thrips live 35 to 40 days.
For specific insecticides and rates, consult the current
Cooperative Extension Service publications on ornamental