Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Host plants
4.16
Trichoplusia ni
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after full moon. There are 3 generations a year in southern California, but
breeding is continuous in the Caribbean (McKinney 1944; Kishaba et al.
1967; Ehler and van den Bosch 1974; Ehler 1977a; Debolt et al. 1984;
Mitchell and Chalfant 1984).
In cotton, a single egg is laid on the underside of a mature leaf in the
upper half of the plant, but seldom in a terminal. On hatching, the larva
generally feeds on the underside of the leaf near the egg, later moving from
leaf to leaf as it passes through 5 instars during 2 to 4 weeks (Ehler 1977a).
Total development time ranges from 19.9 days at 30¡C to 40.4 days at 20¡C
(Jackson et al. 1969). In India at 25¡C the egg stage lasted 2.06 days, the
larval stage of 5 instars 12.38 days, the prepupal 1 day, the pupal 7.27 days
and the adult 7.32 days (Gaikwad et al. 1983). Additional data are provided
by Chi and Tang (1993) and Yadav et al. (1983). Flight and mating activity
are diminished at temperatures less than 16¡C and the threshold for larval
development lies between 10¡C and 13¡C. The larva has 3 pairs of true legs
on the thorax and 3 pairs of fleshy abdominal prolegs near the posterior end.
It crawls by doubling up to form a loop, thus projecting the body forward.
Larvae are green with a white lateral line and 2 whitish lines along the
middle of the dorsal surface. After a brief prepupal period, pupation occurs
in a loosely spun cocoon either on the underside of a leaf or in plant debris at
the soil surface (Ehler 1977a). There is no diapause (Fye 1979).
Eggs and larvae, but also pupae, of T. ni are believed to be readily
transhipped in vegetables and cut flowers (Poe and Workman 1984).
Male T. ni are powerfully attracted to the sex pheromone emitted by
virgin females and will fly long distances upwind under its influence. The
pheromone is produced in a gland situated dorsally between the 8th and 9th
abdominal segments. Six components have been identified and are required
to ensure specificity to T. ni.
The major component is (Z)-7-dodecenyl
acetate, known as looplure, which also attracts males of other looper species.
Looplure, with or without other components, has been used for trapping
males and also in mating disruption experiments. Male T. ni also produce a
pheromone (with at least 3 components) which attracts both females
(especially when starved) and males. ( Bjšstad et al. 1984; McLaughlin
1984; Heath et al. 1992; Dunkelblum and Mazor 1993; Landolt 1995;
Landolt et al. 1996).
In 1966, larvae of T. ni were recorded causing damage to at least 119 species,
varieties and cultivars in 29 families of plants (Sutherland 1966) and that
number has increased steadily over the years to over 160 species in 36